文献名： Structural, morphological and optical properties of Bi NPs obtained by laser ablation and their selective detection of L-cysteine 作者： Ramon Gabriel Teixeira Rosaa, Celso de Araujo Duartea , Wido Herwig Schreinera, Ney Pereira Mattoso Filhoa, Arandi Ginane Bezerra Jr.b, Andersson Barisonc, Fernanda Maria Marins Ocamposc a Departamento de Física, Universidade Federal do Paraná Centro Politécnico, CP 19044, 81531-990 Curitiba (PR), Brazil b Departamento Acadêmico de Física, Universidade Tecnológica Federal do Paraná, 80230-901 Curitiba (PR), Brazil c Departamento de Química, Universidade Federal do Paraná Centro Politécnico, CP 19081, 81531-990 Curitiba (PR), Brazil 摘要：In the present work we show the results of the investigation of the properties of bismuth nanoparticles (NPs) obtained by the laser ablation in water. The samples were characterized by various techniques: UV/vis spectroscopy, dynamic light scattering, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, nuclear magnetic resonance and zeta potential. The NPs were metallic and surface oxidated, exhibiting absorption peak at 257 nm due to the surface plasmon resonance. The interaction between the NPs and various amino acids was studied and revealed a selective sensibility to cysteine on a range of concentration from 80 to 720 μM, which we attribute to a dimerization of cysteine to cystine probably complexed to the nanoparticle surface by electrostatic interactions, leading to the modification of the NP absorption spectrum. 关键词：Bismuth; Nanoparticles; Laser ablation; Cysteine

文献名： Preparation and application of magnetic graphene oxide coated with a modified chitosan pH-sensitive hydrogel: an efficient biocompatible adsorbent for catechin 作者： Hassan Sereshti, Soheila Samadi, Shohreh Asgaria and Maryam Karimia Department of Chemistry, Faculty of Science, University of Tehran, P.O. Box 14155-64555, Tehran, Iran 摘要：In the present study, graft copolymerization of acrylic acid sodium salt (AAS) onto O-carboxymethyl chitosan (O-CMCs) produced a highly hydrophilic and pH-sensitive hydrogel polymer of O-CMCs-g-AAS with a porous surface morphology. The grafted chitosan copolymer was coated on magnetic graphene oxide (MGO) and characterized with TEM, SEM, and FT-IR techniques. The prepared nanocomposite, [O-CMCs-g-AAS]/MGO, was successfully used as an efficient and biocompatible adsorbent in magnetic solid phase extraction (MSPE) coupled with gas chromatography-mass spectrometry (GC-MS) for preconcentration and determination of catechin in tea beverages. The influence of the main parameters affecting the quality of the coating process was investigated and optimized using a response surface methodology. Under the optimum conditions, the adsorbent demonstrated a satisfactory adsorption capacity (27 mg g?1) for catechin and good linearity in the range of 0.005–5 μg mL?1 with a determination coefficient (R2) of 0.9987. The limit of detection (LOD) and limit of quantification (LOQ) were 0.001 and 0.003 μg mL?1, respectively. The relative standard deviation (RSD) was 4.1% (n = 5, C = 0.5 μg mL?1).

Proteins are not only important nutrient source for human society, but also play a crucial role in devising various protein-based therapies for many terminal diseases [1]. Therapeutic proteins are usually administrated by the parenteral route. Their dosage form needs to be formulated either as a solution, a suspension or a reconstituted solid dosage form. Therefore, for protein therapeutic products development, protein hydrodynamic behavior in solutions or suspensions is proven to be much more relevant than its isolated and denatured characteristics revealed via advanced microscopy tech-niques. This can be manifested as either protein size monitoring for QC purposes of its purification processes or their charge property control for optimized formulation stability. The critical requirements for these applications often include, but not limited to, non-invasive (in-situ) nature of measurement techniques, easy-of-use and rapidness of tests. Laser light scattering techniques satisfy these require-ments and provide vital access to the hydrodynamic characteris-tics of biological macromolecules in their native application envi-ronments [2]. Their diffusive displacement (“Brownian” motion) can be quantified as diffusion coefficient with a dynamic light scattering measurement. In turn, their hydrodynamic radius can be calculated. When placed under an electric filed, the charged proteins undergo a uniform translational movement, the so-called electrophoretic motion or electrophoresis. It results in a Doppler phase/frequency shift of the light signal scattered from the moving proteins, which can be quantitatively evaluated with a carefully designed electrophoretic light scattering experiment. From the measured phase/frequency shift, the charge status of proteins can be extracted.

PAMAM dendrimers have recently been investigated as efficient and biocompatible oil dispersants utilizing their encapsulation capacity; however, their high cationic charge density has been shown to be cytotoxic. It is therefore imperative to mitigate cationic charge-induced toxicity and understand the effects of such changes. Presented here is a synergistic experimental and computational approach to examine the effects of varying terminal surface charge on the capacity of dendrimers to disperse model liner, polycyclic aromatic, and hybrid hydrocarbons. Uncharged dendrimers collapse by forming intra-molecular hydrogen bonds, which reduce the hosting capability. On the other hand, changing the surface charges from positive to negative greatly shifts the pKa of tertiary amines of the PAMAM dendrimer interior. As a result, the negatively charged dendrimers have a significant percentage of tertiary amines protonated, ~30%. This unexpected change in interior protonation state cause electrostatic interactions with the anionic terminal groups, leading to contraction and a marked decrease in hydrocarbon hosting capacity. The present work highlights the robust nature of dendrimer oil dispersion and also illuminates potentially unintended or unanticipated effects of varying dendrimer surface chemistry on their encapsulation or hosting efficacy, which is important for their environmental, industrial, and biomedical applications.

We investigated the formation of cocontinuous structures in polymer blends. These polymeric bijels (bicontinuous interfacially jammed emulsion gels) were composed of polystyrene oligomer, polybutene and fluorescent hydrophobic silica nanoparticles. A micron-sized cocontinuous morphology was stabilized by a monolayer of silica nanoparticles at the interface. Real-time observation of coalescence dynamics in co-continuous polymer blends stabilized by interfacial particles was for the first time achieved via laser scanning confocal microscopy. We demonstrated that suppression of coalescence arises from coverage of interfaces by nanoparticles. Furthermore, by combining confocal microscopy with rheology, we correlated the rheological response of a cocontinuous structure with its morphology change. We found that the rheological behavior can be attributed to competition between interface shrinkage and particle network formation. In addition, we showed that a particle scaffold is maintained even after the remixing of two polymer phases above the spinodal point. Finally, we also discussed differences between the shear response of the particle-stabilized cocontinuous structure and normal colloidal gels: the former one is more fragile than the latter under shear.

Let’s answer the question first. To do so, we need to know the size of the Au particle and to assume it is monodisperse. In fact, one purpose of this application note is to explore the meaning of monodispersity, despite its literal definition, one size. We chose 5 nm diameter Au nanoparticles. Now the earth has an average circumference of 40,000 km or 4 x 1016 nm. So we need 8 x 1015 particles. That’s a lot of particles. Yet, it corresponds to a total volume of just 5 x 10-4 cm3, approximately. Gold’s density is 19.3 g/cm3. So we need about 10 mg of Au. Not much. Of course, given that high density, it will be hard to keep the particles from sinking into the oceans as we circumscribe the earth, not to mention the tiny tweezers required to manipulate the nanoparticles. But our main goal is to figure out if the size claimed is correct and if the distribution is one size.

We report observation of both free and defect-mediated excitonic emissions from temperature-dependent PL study on ZnO/graphene oxide (G-O) nanocomposite grown by ultrasonic assisted spray pyrolysis (UASP). From the temperature-dependent photoluminescence (PL) spectra of the ZnO/G-O nanocomposite, new graphene-related peak was observed at 372 nm along with the exciton transition bound to neutral acceptors or deep donors. The PL intensity of new graphene-related peaks (3.33 eV) become more prominent with increasing G-O concentration, and it was saturated or decreased with the addition of >7.0 wt% of G-O. This feature indicates that new graphene-related states were created below conduction band of ZnO, which supports the excitonic PL enhancement by graphene-embedding is contributed not by charge transfer, but by vacancy filling effect of G-O.

Supramolecular polymeric vesicles are constructed by the complexation of p-sulfonatocalix[4]arene and chitosan, where the multivalent electrostatic interactions between the anionic sulfonate tetramer and cationic polyammoniums served as the dominant driving force. The supra-amphiphilic assemblies are disassembled upon exposure to a pH stimulus since the partial deprotonation of chitosan accompanied by a pH increase. Adding a competitive guest can also disrupt the assembly, representing the host–guest inclusion response. Interestingly, an abnormal temperature-response is observed, possibly as a result of the temperature-directed fusion process.

In this paper, a novel pseudostationary phase (PSP), the vesicle formed from octyltriethylammonium bromide (C8NE3Br) and sodium dodecyl benzene sulfonate (SDBS), has been developed in electrokinetic chromatography (EKC). Physicochemical parameters of the mixture of catanionic surfactants such as ζ potential and size of the aggregates were characterized as the molar ratio of C8NE3Br to SDBS varied from 2:8 to 8:2 and total concentration of surfactants fixed at 20 mM. At any ratio mentioned above, ζ potential of mixture of catanionic surfactants remained negative. The absolute values of ζ potential were even larger than in only SDBS system as the molar ratio of C8NE3Br to SDBS less than 4:6, and they decreased as increasing the ratio of cationic surfactants. The size of the aggregates became smaller as the ratio was close to 1. Unexpectedly, the size was smallest at ratio of 3:7 and 6:4, instead of at 5:5. Notably, coagulation did not occur in the catanionic system at any proportion of each other. TEM testified the formation of vesicles. The performance of the vesicle as PSP was evaluated by separating eight kinds of corticosteroids with EKC, these analytes were separated completely without any additives. Compared with SDS microemulsion modified with ionic liquid (IL) and polymeric micelle, the novel vesicle PSP had better separation performances.

Nanoparticle physicochemical properties such as surface charge are considered to play an important role in cellular uptake and particle–cell interactions. In order to systematically evaluate the role of surface charge on the uptake of iron oxide nanoparticles, we prepared carboxymethyl-substituted dextrans with different degrees of substitution, ranging from 38 to 5 groups per chain, and reacted them using carbodiimide chemistry with amine–silane-coated iron oxide nanoparticles with narrow size distributions in the range of 33–45 nm. Surface charge of carboxymethyl-substituted dextran-coated nanoparticles ranged from ?50 to 5 mV as determined by zeta potential measurements, and was dependent on the number of carboxymethyl groups incorporated in the dextran chains. Nanoparticles were incubated with CaCo-2 human colon cancer cells. Nanoparticle–cell interactions were observed by confocal laser scanning microscopy and uptake was quantified by elemental analysis using inductively coupled plasma mass spectroscopy. Mechanisms of internalization were inferred using pharmacological inhibitors for fluid-phase, clathrin-mediated, and caveola-mediated endocytosis. Results showed increased uptake for nanoparticles with greater negative charge. Internalization patterns suggest that uptake of the most negatively charged particles occurs via non-specific interactions.

文献名： Polymeric Suppression of Dopant-Enhanced Surfactant Supramicellar Assemblies 作者： Zifu Zhu and Wayne F. Reed 摘要：Certain hydrophobic dopants in surfactant solutions cause massive “supramicellar assemblies” (SAs) to form near the critical micelle concentration (CMC), characterized by a light-scattering peak (LSP). The SAs are large, dynamic, metastable nanostructures composed of surfactant/dopant. Here, a water-soluble polymer, poly(vinylpyrollidone) (PVP) suppresses SA formation in sodium dodecyl sulfate (SDS) solutions doped with dodecanol, but increases solution instability. Binding of SDS to PVP is stronger than micellization in the LSP regime, reflected in a decreased SA population and a dramatic reduction and inversion of Rayleigh scattering IR as [PVP] increases, since SAs are much more massive than PVP/SDS association structures. Above the LSP regime, SAs no longer exist and thus IR must re-establish its order, increasing with increasing [PVP]. This causes a cross-over in IR vs [SDS] with an “iso-scattering point,” where IR converges at a specific [SDS]. Weak LSP suppression is found using dodecyl tri-ethyl ammonium bromide (DTAB). Poly(ethylene oxide) (PEO)’s effect is small compared with PVP. 关键词：light-scattering peak;supramicellar assemblies;surfactant–polymer interaction

文献名： Temperature and pH sensitive hydrogels: An approach towards smart semen-triggered vaginal microbicidal vehicles 作者： Kavita M. Gupta, Scott R. Barnes, Rachel A. Tangaro, Meredith C. Roberts, Derek H. Owen, David F. Katz andPatrick F. Kiser 摘要：Microbicides are drug delivery systems (DDSs) for the prevention of sexual transmission of HIV and other STDs. A topically applied vaginal microbicidal gel should provide uniform coating of vaginal tissue, retention of this gel layer prior to intercourse, and controlled release kinetics of antivirals to inactivate the viral load potentially introduced during sexual activity. Here, we describe the microbicide-oriented characterization of a DDS made with a dual pH sensitive and thermosensitive smart polymer gel composed of a random terpolymer of N-isopropyl acrylamide, butyl methacrylate, and acrylic acid. The system was engineered to coat vaginal tissue with a stable gel layer and to release entrapped model agents in a burst release profile in response to the presence of the infecting agent: semen. The gel rheology, layer erosion properties, model drug release kinetics, and cytocompatibility of the terpolymer system were studied. Negligible erosion of the gel in the presence of vaginal fluid simulant suggests prolonged retention. Burst release of molecular and macromolecular model compounds was observed when the system's pH changed from the vaginal pH to the pH of semen, and cytotoxicity studies showed that the terpolymer is equally cytocompatible as a commonly used polymeric vaginal carrier. 关键词：HIV/AIDS;microbicide;formulation vehicle;viscosity;thermal gels;responsive delivery system;semen-triggered drug release;controlled release/delivery;vaginal coating;retention

Morphological and conformational transitions of lentinan (LT), a ˇ-glucan extracted from Shiitake mush-rooms (Lentinula edodes), were investigated at different concentrations of aqueous NaOH, using SmallAngle X-ray Scattering (SAXS) technique. At low NaOH(aq)concentration LT chains are self-associatedand adopt the triple helix form where as at higher NaOH concentrations the polymer chains undergo atransition to random coil chains. Also, the presence of fractal dimensions was observed through analysisof the exponential decay of the scattering intensity as a function of the scattering angle. In addition, thelateral radius of gyration was determined for LT in different concentrations of NaOH solution, indicating arigid triple helix present as a small rod-like structure. Interactions of LT with two zwitterionic surfactantswere investigated by surface tension, fluorescence, and static light scattering measurements. Experimen-tal data showed that the formation of LT–(surfactant) complexes occurred through a cooperative process.

文献名： Adsorption of copolymers aggregates: From kinetics to adsorbed layer structure 作者： Bogdan Zdyrkoa, Pazit Bar-Yosef Ofira, Alina M. Albb, Wayne F. Reedb, Maria M. Santorea, a Department of Polymer Science and Engineering, University of Massachusetts, 120 Governors Drive, Amherst, MA 01003, USA b Department of Physics, Tulane University, New Orleans, LA 70118, USA 摘要：We examined the adsorption, on hydrophobic and hydrophilic surfaces, of 4 rake-type poly(dimethyl siloxane) (PDMS) copolymers varying the amount of poly(ethylene glycol) (PEG) graft arms from 41 to 72%. The copolymers formed large aggregates in solution, complicating their adsorption kinetics and layer structures. We found the adsorption process always to be dominated by the adsorption of large aggregates, with strongly bound layers resistant to rinsing in adsorbing buffer. Adsorbed amounts were nearly independent of the substrate. However, subtleties in the adsorption kinetics suggested different layer structures for the different systems. On hydrophilic silica, aggregates adsorbed at the transport limited rate until surface saturation, and associated interfacial structures were likely retained. On the hydrophobic surface, a subset of the copolymers exhibited retarded late stage adsorption kinetics suggestive of brush formation. This work demonstrates how subtle differences in adsorption kinetics provide insight into potential interfacial layer structures. 关键词：Polymer brush adsorption; Aggregate adsorption; Micelle adsorption; Associated adsorbed layer; Mushroom layer; Adsorbed copolymers; Copolymer layers; Adsorption kinetics

文献名： Hydrophobic microblock length effect on the interaction strength and binding capacity between a partially hydrolyzed microblock hydrophobically associating polyacrylamide terpolymer and surfactant 作者： Yongjun Guo, Yan Liang, Xueshan Yang, Rusen Feng, Rutong Song, Jingda Zhou and Feilong Gao 摘要：Poly(acrylamide/sodium acrylate/N-dodecyl acrylamide)s [poly(AM/NaAA/C12AM)s] with different hydrophobic microblock lengths (NH's) were prepared by the micellar copolymerization of acrylamide and sodium acrylate with a low amount of N-dodecyl acrylamide (0.2 mol %), and the molecular structure was characterized by Fourier transform infrared spectroscopy, 1H-NMR, and static light scattering. A combination of experiments involving viscosity measurement, fluorescence, and conductometry was applied to investigate the effect of NH on the interaction strength and binding capacity between poly(AM/NaAA/C12AM)s and C12H25SO4Na [sodium dodecyl sulfate (SDS)]. The viscosity, I3/I1 (the intensity ratio of the third vibrational band to the first band of pyrene molecules), and conductivity of the mixed system of copolymers with SDS all had different variation trends with the concentration of SDS. The binding capacity of the copolymers with SDS was calculated according to quantitative differences between the critical micelle concentration of the pure SDS solution and the mixed system. All of the results show that the interaction strength of SDS with the copolymers rose, and the binding capacity decreased with increasing NH. 关键词：copolymers;electrochemistry;spectroscopy;surfactants;viscosity and viscoelasticity

文献名： Online Monitoring of Copolymerization Involving Comonomers of Similar Spectral Characteristics 作者： Alina M. Alb , Pascal Enohnyaket , Michael F. Drenski , Aaron Head , Alex W. Reed , and Wayne F. Reed Physics Department, Tulane University, New Orleans, Louisiana 70118 摘要：Automatic continuous online monitoring of polymerization reactions (ACOMP) was applied to free radical copolymerization of acrylic comonomers, whose spectral characteristics are very similar. Determination of the instantaneous concentration of each comonomer during the reaction was made possible by incorporating a full spectrum UV spectrophotometer into the detector train. The working assumption was that a UV spectrum at any instant during conversion is a linear combination of the normalized basis spectra of the comonomers and the copolymer, and that the unknown comonomer concentrations can be found by minimizing the error between measured and computed spectra over many wavelengths, even when spectral differences are small at any given wavelength. Here, the copolymerization of butyl acrylate (BA) and methyl methacrylate (MMA) was monitored under different starting composition ratios. Continuous conversion kinetics, composition drift, and average composition distribution are all found from the data, in addition to the evolution of weight-average intrinsic viscosity and molar mass Mw. Reactivity ratios, rmma = 0.40 ± 0.05 and rba = 2.58 ±0.1, are close to the averages found from a literature survey over a wide range of conditions. Comonomer conversion results were independently cross-checked by GPC. Increasing the content of BA in the copolymer was found to increase Mw, while also leading to a significant increase in chain stiffness. This work sets the stage for extension to copolymerization of three and more comonomers.

Unstable biopolymer solutions inevitably lead to mis-characterization of macromolecular properties and irreproducible results. Even under stable or quasi-stable conditions, persistent aggregates can hamper reliable characterization, especially using light scattering methods. Various pitfalls in characterizing biopolymers were worked through, including determination of solution stability zones, dissolution kinetics, estimation of fraction of aggregate populations, and the relationship between batch and fractionation methods. Chitosans, polyampholytic biopolymers with isoelectric point around pH = 6.0, with varying degrees of carboxymethylation were studied. Instability was determined vs. pH and ionic strength using a high throughput screening method, simultaneous multiple sample light scattering (SMSLS). With stable solution conditions determined, equilibrium batch and multi-detector GPC characterization of molecular weight, intrinsic viscosity, and polyelectrolyte properties was made. Finally, a first attempt at continuous online monitoring of the modification reaction itself was made and compared to FTIR analysis of carboxymethylation on discrete aliquots. Given the range of possible characterization problems, multiple approaches with independent instruments may be required for reliable natural product characterization. Online monitoring of modification reactions may lead to rapid advances in understanding and preparation of natural products.

Electrostatic interactions between synthetic polyelectrolytes and proteins can lead to the formation of dense, macroion-rich liquid phases, with equilibrium microheterogeneities on length scales up to hundreds of nanometers. The effects of pH and ionic strength on the rheological and optical properties of these coacervates indicate microstructures sensitive to protein?polyelectrolyte interactions. We report here on the properties of coacervates obtained for bovine serum albumin (BSA) with the biopolyelectrolyte chitosan and find remarkable differences relative to coacervates obtained for BSA with poly(diallyldimethylammonium chloride) (PDADMAC). Coacervation with chitosan occurs more readily than with PDADMAC. Viscosities of coacervates obtained with chitosan are more than an order of magnitude larger and, unlike those with PDADMAC, show temperature and shear rate dependence. For the coacervates with chitosan, a fast relaxation time in dynamic light scattering, attributable to relatively unrestricted protein diffusion in both systems, is diminished in intensity by a factor of 3?4, and the consequent dominance by slow modes is accompanied by a more heterogeneous array of slow apparent diffusivities. In place of a small-angle neutron scattering Guinier region in the vicinity of 0.004 ?-1, a 10-fold increase in scattering intensity is observed at lower q. Taken together, these results confirm the presence of dense domains on length scales of hundreds of nanometers to micrometers, which in coacervates prepared with chitosan are less solidlike, more interconnected, and occupy a larger volume fraction. The differences in properties are thus correlated with differences in mesophase structure.

This paper describes the facile synthesis and bioevaluations of a novel conjugated polymer having tetrasaccharide SLeX branch and chitosan backbone (SLeX–chitosan conjugate). The synthesis was achieved by a convenient chemoenzymatic approach using an aldehyde-functionalized N-acetylglucosamine to branch it onto chitosan amino groups followed by three enzymatic reactions to further append galactose, sialic acid, and fucose residue to the branch. Surface plasmon resonance (SPR) study of SLeX–chitosan conjugate revealed a high affinity binding with E-selectin (Kd = 920 nM) and a potent inhibitory effect on the binding of E-selectin with SLeX–BSA (IC50 = 240 μM). By using biocompatible chitosan as the scaffold for presenting SLeX ligands, as well as the concise route tailored for the conjugate syntheses, the present study provides a practical method to explore safe and efficient anti-inflammatory agents.

Chitosan and polyacrylic acid (PAA) both have weak, short-lasting bioadhesive properties; therefore, a hybrid particle composed of a chitosan derivative and PAA could be used as a new bioadhesive agent. Using simultaneous in-situ monitoring with a multidetection system, N-carboxymethyl chitosan was ionically bonded to acrylic acid and then polymerized using potassium persulphate as the initiator (N-CMCA-Dh of 165 nm). The PAA on N-CMCA was crosslinked using N,N-methylene-bisacrylamide (N-CMCAC-Dh of 141 nm). During polymerization, the solution developed a milky white appearance, and polymerization kinetics was determined to be 3.2 × 10?3 ± 4.0 × 10?6 mmol/min. The reaction for PAA alone was 1.7 times faster than that of the hybrid system. The particles showed an increase in thermal stability and reduction of thermal-mass loss compared with the N-CMC alone. The N-CMCAC particles showed the highest bioadhesion onto the stomach. The gastroprotection index of N-CMChAC particles against ethanol/HCl-induced ulcers in mice was 68.2 ± 6.4%. Similar results were observed for omeprazole (74.2 ± 5.3%). The particles obtained in this work have potential for use in drug delivery to the stomach, perhaps to aid in treating ulceration and inflammation, and can be used as a system for the prevention of ethanol-induced ulcers.

Magnetic nanoparticles consisting of iron oxide cores modified with covalently linked chitosan oligosaccharide (CSO) that are colloidally stable in water and buffers were obtained. Primary oleic acid coated nanoparticles were synthesized through the thermal decomposition method and the surface ligand exchanged to a carboxylic acid silane. Amide linkage between the chitosan and magnetic nanoparticles was obtained through carbodiimide activation, under conditions which promoted particle stability and chitosan solubility. Magnetic measurements indicate that the particles are superparamagnetic. Measurements of hydrodynamic diameter and zeta potential, coupled with TEM measurements, indicated that CSO coated nanoparticles consist of single primary particles coated with a chitosan corona. These nanoparticles are stable in water for a wide range of pH, and in commonly used biological buffers, such as phosphate buffered saline (PBS), Hank's balanced salt solution (HBSS), and Dulbecco's modified eagle's medium (DMEM) with fetal bovine serum (FBS).

Reversible addition fragmentation transfer (RAFT) belongs to the group of the controlled radical polymerization (CPR) methods, intensively employed in the synthesis of polymers with complex architectures and structures. pHresponsive amphiphilic copolymers synthesized by RAFT, lead to materials with versatile properties. Optimization of the reaction kinetics during RAFT polymerization of 2-(dimethylamino)ethyl acrylate (DMAEA) in N,Ndimethylformamide (DMF) was investigated in this study, followed by the synthesis of DMAEA/styrene amphiphilic diblock copolymers, using Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP). Poly(DMAEA) is a pH sensitive polymer with wide applications in pharmaceutical and water treatment industries yet challenging due to possible interaction of its amino group with catalysts.

Artemisia seed polysaccharide (ASP) has great potential to be used as stabilizer, water retention agent and filmogen due to its high viscosity. This study reports analyses of its composition and molecule weight using gas chromatography (GC) and light scattering techniques. The molecular structure of the ASP at different concentrations was observed with atomic force microscopy (AFM). The relationship between structural and physical characteristics of ASP was also described in details. Our results showed that the ASP was composed of l-arabinose (l-Ara), d-xylose (d-Xyl), d-lyxose (d-Lyx), d-mannose (d-Man), d-glucose (d-Glu) and d-galactose (d-Gal). Its molecular weight was about 1.42 × 105. The ASP molecule had a linear backbone with branches. The network structure of ASP was formed through entanglement between the molecules of the polysaccharide.

Polyacrylate glue protein analogs of the glue secreted by Phragmatopoma californica, a marine polycheate, were synthesized with phosphate, primary amine, and catechol sidechains with molar ratios similar to the natural glue proteins. Aqueous mixtures of the mimetic polyelectrolytes condensed into liquid complex coacervates around neutral pH. Wet cortical bone specimens bonded with the coacervates, oxidatively crosslinked through catechol sidechains, had bond strengths nearly 40% of the strength of a commercial cyanoacrylate. The unique material properties of complex coacervates may be ideal for development of clinically useful adhesives and other biomaterials.

Reversible addition fragmentation transfer (RAFT) belongs to the group of the controlled radical polymerization (CPR) methods, intensively employed in the synthesis of polymers with complex architectures and structures. 1,2 pHresponsive amphiphilic copolymers synthesized by RAFT, lead to materials with versatile properties. Optimization of the reaction kinetics during RAFT polymerization of 2-(dimethylamino)ethyl acrylate (DMAEA) in N,Ndimethylformamide (DMF) was investigated in this study, followed by the synthesis of DMAEA/styrene amphiphilic diblock copolymers, using Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP). Poly(DMAEA) is a pH sensitive polymer with wide applications in pharmaceutical and water treatment industries yet challenging due to possible interaction of its amino group with catalysts.3,4

ACOMP allows comprehensive, model-independent, near realtime monitoring of many different types of polymerization reactions. It provides conversion kinetics, and the evolution of average molar mass, intrinsic viscosity and average composition distributions (for copolymers). Here, recent advances in ACOMP will be summarized, dealing with continuous reactors, copolymerization, ‘living’ type reactions (NMP, RAFT, ATRP, ROMP), polyelectrolytes, heterogeneous phase reactions, including free radical reactions in emulsions, and predictive control. In the case of emulsion polymerization, a new approach will be presented in which the evolution of the characteristics of both the soluble phase – monomer conversion, polymer molar mass and intrinsic viscosity- and the dispersed phase – particle size – are simultaneously monitored. NSF CBET 0623531, BoR ITRS 019B, NASA NCC3-946, TIMES, PolyRMC (Tulane Center for Polymer Reaction Monitoring and Characterization).

Using automatic, continuous online monitoring of polymerization reactions (ACOMP) the final, divergent growth phase (FDGP) of the condensation polymerization of dimethylamine, epichlorohydrin, and ethylenediamine was monitored, which produced a highly ramified, polyelectrolytic polyamine. The weight average mass, Mw, increased exponentially during the FDGP, whereas weight averaged intrinsic viscosity [è]w increased slowly, reaching a plateau. Multi-detector gel permeation chromatography (GPC) revealed that polymers of mass 20 000 to 106 are branched and self-similar, but above this mass, [è] increases less strongly with M. This appears to be due to higher order ramification, a precursor to gelation. The ACOMP trends in Mw and [è]w provide direct online evidence of this process. It is shown computationally that a mere increase in polydispersity cannot explain this behavior. GPC showed the mass distribution becomes highly asymmetric as conversion increases. A plausible kinetic model for the distribution asymmetry is introduced, and a complementary model for the effects of higher order ramification on [è]w.

The human pathogenic fungus Cryptococcus neoformans has a large polysaccharide (PS) capsule a copious amounts of PS into cultures and infected tissues. The capsular PS is a major virulence fact elicit protective antibody responses. PS recovered from culture supernatants has historically provid and convenient source of material for structural and immunological studies. Two major assumption studies are that the structural features of the exopolysaccharide material faithfully mirror those of c that the isolation methods do not change PS properties. However, a comparison of exopolysacchari two isolation techniques with capsular PS stripped from cells with gamma radiation or dimethyl su revealed significant differences in glycosyl composition, mass, size, charge, viscosity, circular-dich and reactivity with monoclonal antibodies. Our results strongly suggest that exopolysaccharides an are structurally different. A noteworthy finding was that PS made by cetyltrimethylammonium bro precipitation had a larger mass and a different conformation than PS isolated by concentration and suggesting that the method most commonly used to purify glucuronoxylomannan alters the PS. He method used to isolate PS can significantly influence the structural and antigenic properties of the p findings have important implications for current views of the relationship between capsular PS and exopolysaccharides, for the generation of PS preparations suitable for immunological studies, and f formulation of PS-based vaccines for the prevention of cryptococcosis.

In situ near infrared (NIR) spectroscopy is performed simultaneously with automatic continuous online monitoring of polymerization reactions (ACOMP) during methyl methacrylate polymerization. ACOMP is an absolute technique that furnishes weight average molecular mass Mw, intrinsic viscosity, monomer conversion, and other characteristics, whereas NIR furnishes monomer conversion data via an empirical calibration. An advantage of in situ NIR is that it furnishes immediate information on the conversion in the reactor, whereas ACOMP relies on continuous withdrawal and dilution of a small stream of reactor fluid, so that there is a lag time of several minutes between what ACOMP reports and what is occurring in the reactor. Simultaneous monomer conversion data from in situ NIR and ACOMP, the latter derived from both refractive index and UV absorption, are compared and found to be in good agreement. The evolution of conversion kinetics and Mw generally conform to the predictions of the Quasi-Steady State Approximation. Having established the agreement between the methods, the path is now open for combining NIR with ACOMP to characterize increasingly complex systems, such as copolymerization with two or more monomeric species, that are not feasible by either technique separately.

Unstable biopolymer solutions inevitably lead to mis-characterization of macromolecular properties and irreproducible results. Even under stable or quasi-stable conditions, persistent aggregates can hamper reliable characterization, especially using light scattering methods. Various pitfalls in characterizing biopolymers were worked through, including determination of solution stability zones, dissolution kinetics, estimation of fraction of aggregate populations, and the relationship between batch and fractionation methods. Chitosans, polyampholytic biopolymers with isoelectric point around pH=6.0, with varying degrees of carboxymethylation were studied. Instability was determined vs. pH and ionic strength using a high throughput screening method, simultaneous multiple sample light scattering (SMSLS). With stable solution conditions determined, equilibrium batch and multi-detector GPC characterization of molecular weight, intrinsic viscosity, and polyelectrolyte properties was made. Finally, a first attempt at continuous online monitoring of the modification reaction itself was made and compared to FTIR analysis of carboxymethylation on discrete aliquots. Given the range of possible characterization problems, multiple approaches with independent instruments may be required for reliable natural product characterization. Online monitoring of modification reactions may lead to rapid advances in understanding and preparation of natural products.