Content Of Copolymers Research Articles

Structure–property relationships and constitutive viscoelastic behaviors of polyether‐block‐amide elastomers in melt and solid states

AbstractIn this study, effects of copolymer composition on the structural, thermal, and viscoelastic properties of segmented multi‐block polyamide elastomers (PEBAX® 3533, 5533, and 6333) and polyamide‐12 (PA12) were quantified by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, and dynamic mechanical analysis (DMA) methods and rheological measurements. Soft segment, poly(tetramethylene oxide) (PTMO), contents of copolymers were proved by FTIR analysis. It was found that the increase in PTMO content dramatically reduced the crystallization and melting temperatures and degree of crystallinity values of copolymers. Different rheological test protocols performed in melt state revealed that zero shear rate viscosity values of polyamide elastomers increased with the increasing amount of hard segment. On the other hand, increase in hard segment content yielded lower flow activation energy value. In this study, we mainly focused on understanding quantitative relationships between block copolymer structure and their rheological behaviors and found that the soft segment content of ~40 (mole %) is the critical point for changing the rheological behaviors of block copolymer PAEs, dramatically. DMA measurements implied that the solid‐state viscoelastic behaviors of samples were governed by the hard content of copolymers. Higher hard content decreased long‐term creep strain and creep rate.

Tailored fluorinated oligo-polystyrene as efficient additive for the hydrophobicity/oleophobicity improvement of styrenic polymers

• Perfluorinated polystyrene copolymers were designed and developed as functional additives. • Various fluorinated additives with fluorinated monomer content were synthetized. • The functionality of all synthetized copolymers was validated. • Significant Improvement of hydrophobic and oleophobic surface properties of polystyrene. The surface properties improvement results from both the presence of fluorine and the morphology. • The additive with 19 mol.% of fluorinated monomer has a homogeneous morphology. • The additive with 19 mol.% allows the achievement of higher contact angles. The hydrophobic and oleophobic surface properties of polystyrene can be improved by using specific perfluorinated polystyrene copolymers as additives. In this work, an efficient synthetic route consisting in chemical modification via nucleophile substitution of chlorinated copolymers precursors was optimized. FTIR, 1 H NMR, 13 C NMR and 19 F NMR spectroscopic techniques were used to verify the overall conversion of reactions, characterize the chemical structures and quantify the composition of fluorinated part in the synthetized copolymers. Additionally, the thermal characterizations performed by Differential Scanning Calorimetry and the microstructure revealed by Optical Microscopy and X-ray diffraction, evidenced that the copolymer based on 19 mol.% of fluorinated monomer exhibits a singular properties and seems closer to a periodic copolymer conformation. These singular properties would originate from an interpenetrating conformation and explain the homogeneous morphology for all formulations based on this copolymer in comparison with copolymers based on 4 and 37 mol.% of fluorinated monomer. Finally, the functionality of the synthetized copolymers was evaluated, by measurement of water/oil static contact angles, and also in blend with a commercial polystyrene matrix at various wt.% of additives ranging from 100 ppm to 100 %. The effects of nature and content of copolymers on the hydrophobic and oleophobic surface properties were investigated. For all copolymers, the more the additive content increases, the more the surface properties are improved, obeying a threshold behavior for 4 and 37 mol.% and a quasi-linear behavior for 19 mol.%. Finally, it was evidenced that the surface properties improvement results both from the presence of a critical percentage of fluorine in the polymers blends and its consequence on the morphological properties. The additive based on 19 mol.% of fluorinated monomer allowing the achievement of higher static contact angles even with very low percentages of additive was identified as an optimal additive for improvement of polystyrene surface properties.

A novel membrane with ion-recognizable copolymers in graphene-based nanochannels for facilitated transport of potassium ions

Facilitated transport of K+ ions through membranes is of great significance in both science and technology for the efficient and selective separation of potassium ions. Here, a novel membrane with ion-recognizable copolymers in graphene-based nanochannels is developed for facilitated transport of potassium ions. The poly(N-isopropylacrylamide-co-benzo-15-crown-5-acrylamide) (PNB) copolymers are fixed in the lamellate spacings between the partially reduced graphene oxide (prGO) nanosheets. The K+ permeability of the fabricated prGO-PNB membrane remarkably increases at around the lower critical solution temperature (LCST) of the PNB copolymer, because of the dynamic complexation between B15C5 units and K+ ions at around the LCST. The selectivity of K+/Na+ increases with increasing the content of PNB copolymers in the membrane. The proposed membrane shows good stability in water and K+ separation performance. Due to the uniform channels and facilitated transport mechanism of the prGO-PNB membrane, the comprehensive performance of selectivity and permeability of the K+ ions is better than that of previously reported polymer-based nanofiltration membranes, polymer-based facilitated transport membranes and graphene-based membranes. The proposed strategy of this prGO-PNB membrane that combining graphene-based sheets as “skeleton” and substance-recognizable copolymers as “facilitators” is also applicable to fabricate membranes for facilitated transport of other ions or molecules.

Polysulfone‐based amphiphilic copolymers: Effect of hydrophilic content on morphology and performance of ultrafiltration membranes

ABSTRACTA series of polysulfone (PSf)‐based amphiphilic graft copolymers were synthesized to investigate the effects of copolymer composition on membrane morphology and performance. PSf‐based ultrafiltration membranes were prepared by phase inversion method using the blends of PSf and PSf‐g‐poly(ethylene glycol) methyl ether methacrylate (PEGMA) copolymers. Membranes were evaluated in terms of pure water permeability, flux recovery ratio (FRR), protein rejection, and contact angle. The morphology of the membranes was investigated by scanning electron microscopy. Contact angle of membranes was decreased from 85.7° to 51.6°, while the FRR was greatly increased from 55 to 95% upon increasing the PEGMA content of copolymers from 20 to 70 wt %. Results indicated that the ratio of hydrophilic/hydrophobic segments in amphiphilic structures is one the key parameters that control the phase inversion process by altering miscibility, viscosity, and wettability of casting solutions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48306.

Antimicrobial Porous Surfaces Prepared by Breath Figures Approach.

Herein, efficient antimicrobial porous surfaces were prepared by breath figures approach from polymer solutions containing low content of block copolymers with high positive charge density. In brief, those block copolymers, which were used as additives, are composed of a polystyrene segment and a large antimicrobial block bearing flexible side chain with 1,3-thiazolium and 1,2,3-triazolium groups, PS54-b-PTTBM-M44, PS54-b-PTTBM-B44, having different alkyl groups, methyl or butyl, respectively. The antimicrobial block copolymers were blended with commercial polystyrene in very low proportions, from 3 to 9 wt %, and solubilized in THF. From these solutions, ordered porous films functionalized with antimicrobial cationic copolymers were fabricated, and the influence of alkylating agent and the amount of copolymer in the blend was investigated. Narrow pore size distribution was obtained for all the samples with pore diameters between 5 and 11 µm. The size of the pore decreased as the hydrophilicity of the system increased; thus, either as the content of copolymer was augmented in the blend or as the copolymers were quaternized with methyl iodide. The resulting porous polystyrene surfaces functionalized with low content of antimicrobial copolymers exhibited remarkable antibacterial efficiencies against Gram positive bacteria Staphylococcus aureus, and Candida parapsilosis fungi as microbial models.

Preparation of injectable hydrogels from temperature and pH responsive grafted chitosan with tuned gelation temperature suitable for tumor acidic environment

In this present work, stimuli responsive polymers that can respond to the temperature and pH of the environment were prepared. A series of temperature responsive diblock copolymers based on poly(ethylene glycol) methyl ether (mPEG) and ε-caprolactone (CL) were synthesized. Subsequently, the diblock copolymers were grafted onto chitosan, a pH responsive biopolymer. These chitosan-graft-(mPEG-block-PCL) (chitosan-g-(mPEG-b-PCL)) graft copolymers were structurally characterized by 1H NMR and FTIR and their sol-gel phase transitions were analyzed by the test tube inversion method as well as dynamic rheological measurements. These chitosan-g-(mPEG-b-PCL) graft copolymers demonstrated tunable temperature and pH responsive sol-gel phase transitions that correspond well with body temperature and pH of acidic tumor microenvironments. Gelation temperature (Tgel) decreased with increasing pH of the system, increasing PCL composition in the diblock copolymers, increasing solution concentration and decreasing grafting content of the diblock copolymers on chitosan. The graft copolymer hydrogels successfully showed the sustained release of both doxorubicin and curcumin for up to 2 weeks. The designed system was based on chitosan-g-(mPEG-b-PCL) graft copolymers, of which chitosan showed pH responsive properties and mPEG-b-PCL acted as a temperature sensitive moiety. In addition, mPEG and PCL are recognized as biocompatible polymers and chitosan has been engaged in various pharmaceutical research. Thus, this system could be considered an alternative choice for drug delivery applications.

Self-assembly of L-proline functional thermoresponsive double hydrophlic block copolymers for aldol reaction in water: the influence of POEGA block content

The self-assembly of L-proline functional thermoresponsive double hydrophlic block copolymers (DHBCs) can effectively catalyze aldol reaction in water. Considering the block content of copolymers influences the assemblies and catalytic activities, thermoresponsive DHBCs supported L-proline P(NIPAm-co-ProlA)-b-POEGA with different POEGA block content were prepared by reversible addition fragmentation chain transfer (RAFT) polymerization. The therm-triggered self-assemblies were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Then, the resultant assemblies were used as catalysts for the aldol reaction with cyclohexanone and 4-nitrobenzaldehyde as substrates. The results indicated that P(NIPAm-co-ProlA)-b-POEGA with ca. 18 mol% of POEGA can form stable catalytic system, which maintained high selectivity and productivity of product, accompanied with satisfactory reusability.

INVESTIGATION OF INTERACTION OF BROMPHENOL SYNTHES WITH CATIONIC POLYACRYLAMIDES AND APPLICATION OF IT IN THE ANALYSIS

The aim of this work was to study the interaction of bromophenol blue with cationic polyacrylamides and the development on this basis of a simple, rapid and highly sensitive technique for determining the content of copolymers of acrylamide and the chloromethylated polymer in waters containing moderate amounts of strong electrolytes. The changes in the spectra are similar to those observed for the same dyes in the presence of cationic surfactant micelles. It is shown that two types of effects appear in the presence of polymers: the shift of the acid-base equilibrium caused by the formation of the ionic associate polymer-dye and the aggregation of the dye. Optimal conditions for the formation of the ion associate are established. The presence of salts in concentrations above the critical leads to a decrease in light absorption, the appearance of a negative systematic error. The application of the photometric titration method makes it possible to compensate to a certain extent the interfering effect of inorganic ions. In the presence of inorganic salts, the shape of the photometric titration curve near the end point of the titration is washed out, but its position remains practically unchanged, which makes it possible to determine the polymer flocculant in the presence of not very large concentrations of inorganic salts. Spectrophotometric methods for determining the content of CPAA FO in production solutions or natural waters with a low level of mineralization by methods of a calibration curve and photometric titration have been developed. Method of a calibration curve allow allows to determine polymer in the range of concentrations 0,12 –1,8 μg/L. The limit of determination of CPAA FO is 0.088 μg/L. The methods are tested on artificial mixtures and artesian water.

Simultaneous determination of the styrene unit content and assessment of molecular weight of triblock copolymers in adhesives by a size exclusion chromatography method.

The content of styrene units in nonhydrogenated and hydrogenated styrene-butadiene-styrene and styrene-isoprene-styrene triblock copolymers significantly influences product performance. A size exclusion chromatography method was developed to determine the average styrene content of triblock copolymers blended with tackifier in adhesives. A complete separation of the triblock copolymer from the other additives was realized with size exclusion chromatography. The peak area ratio of the UV and refraction index signals of the copolymers at the same effective elution volume was correlated to the average styrene unit content using nuclear magnetic resonance spectroscopy with commercial copolymers as standards. The obtained calibration curves showed good linearity for both the hydrogenated and nonhydrogenated styrene-butadiene-styrene and styrene-isoprene-styrene triblock copolymers (r=0.974 for styrene contents of 19.3-46.3% for nonhydrogenated ones and r=0.970 for the styrene contents of 23-58.2% for hydrogenated ones). For copolymer blends, the developed method provided more accurate average styrene unit contents than nuclear magnetic resonance spectroscopy provided. These results were validated using two known copolymer blends consisting of either styrene-isoprene-styrene or hydrogenated styrene-butadiene-styrene and a hydrocarbon tackifying resin as well as an unknown adhesive with styrene-butadiene-styrene and an aromatic tackifying resin. The methodology can be readily applied to styrene-containing polymers in blends such as poly(acrylonitrile-butadiene styrene).

Synthesis, properties and degradation of polyisobutylene-polyester graft copolymers

The development of copolymers is a promising approach for combining the favorable properties of two polymers and obtaining new properties of the combination. In this work, graft copolymers of polyisobutylene (PIB) and polycaprolactone or poly(d,l-lactide) were synthesized and studied. Amine-terminated polyesters were synthesized and were grafted onto an activated PIB backbone synthesized from butyl rubber, a copolymer of isobutylene and 2 mol% isoprene. The polyester content was tuned from 15 to 44 wt% by varying the molar mass of the polyester blocks and the number of molar equivalents used in the grafting reaction. The graft copolymers with higher polyester content underwent nanoscale phase separation, as demonstrated by differential scanning calorimetry and atomic force microscopy imaging. This was found to provide enhanced mechanical properties such as increased tensile strength and Young's modulus relative to the starting rubber or physical blends. Despite the significant polyester content of the graft copolymers and the susceptibility of the polyesters to degradation, the graft copolymers underwent negligible mass loss in 5 mol L−1 NaOH over a period of eight weeks. These results suggest that polyesters can be incorporated into PIB to tune and enhance its properties, while maintaining high chemical stability. © 2016 Society of Chemical Industry

Influences of three different ethylene copolymers on the toughness and other properties of polylactide

The aim of this study was to investigate influences of three different ethylene copolymers on the toughness and other properties of very brittle biopolymer PLA (polylactide). For this aim, PLA was melt blended by twin-screw extruder with various amounts of ethylene vinyl acetate (EVA), ethylene-methyl-acrylate (EMA) and ethylene-n-butyl acrylate-glycidyl-methacrylate (EBA-GMA). SEM and DSC analyses indicated that these ethylene copolymers were thermodynamically immiscible with phase separation in the form of 1–5 µm sized round domains in the PLA matrix. Rubber toughening mechanisms of EVA, EMA and EBA-GMA were very effective to improve ductility and toughness of PLA significantly. Depending on the type and content of the ethylene copolymers, the highest increases in % elongation at break, Charpy impact toughness and GIC fracture toughness values of PLA were as much as 160, 320 and 158%, respectively. Although there were no detrimental effects of using EVA, EMA and EBA-GMA on the thermal properties of PLA, they resulted in certain level of reductions in stiffness, strength and hardness values.

RELATIONSHIP BETWEEN CONTACT ANGLE HYSTERESIS AND WORK OF ADHESION OF OIL DROPLETS ON PERFLUOROMETHACRYLATESTYRENE THIN FILMS

Water and oil repellencies of flat films are crucial properties of solid materials and some biomimetric surfaces that significantly depend on surface topography and chemical compositions [1,2]. The surface wettability is expressed indirectly by the contact angle (CA) measurements of a specific liquid droplet on these surfaces [1-4]. However, in practical systems, measurement of only equilibrium CA (θe) is not enough to explain polymer surface characteristics, so advancing (θa), receding (θr) CA’s and thus the contact angle hysteresis (CAH= θa – θr) are required to accurately characterize the dewetting properties of the surfaces [1-9]. CAH of a surface is strongly affected from surface chemical heterogeneity and roughness. In addition, the relationship between the equilibrium and dynamic states (work of adhesion, Wa and CAH) is also an important parameter for the characterization of solid surfaces. Basically, the estimate of drop movement on a surface can be represented by Wa values, i.e., a higher Wad value causes a higher tendency of the droplet to stick on the tilt surface. In this study, the oil repellencies of flat perfluoroethyl alkyl methacrylate-styrene (Zonyl-TM-S) random copolymers, which were synthesized in a CO2-expanded monomer medium at 250 bar pressure and 80 oC were investigated with various perfluoroethylalkyl contents. Flat and transparent copolymer surfaces were formed by using dip-coated on glass slides from THF as solvent. The increase in the perfluoromethacrylate content of the flat copolymers resulted in a decrease of the total surface free energy of the flat copolymer surfaces from 19.0 to 14.2 mJ/m2. The oil repellencies of (Zonyl-TM-S) copolymers in the terms of contact angle hysteresis was compared with perfluoroethyl alkyl methacrylate-methyl methacrylate copolymer (Zonyl-TM-ran-MMA) by using oil drops with varying surface tensions between 20.9 mN/m and 26.9 mN/m. The effect of liquid surface tension and wt.% content of Zonyl-TM on oleophobicities of the surfaces were also examined. Increase in hydrocarbon chain lengths also caused an increase in the measured CA values due to the weaker adhesion interactions between the liquid drop and the solid surface. Increase in wt.% Zonyl-TM content of the copolymers resulted in a decrease in Wa values due to the increase of fluorine atoms in copolymer surfaces. The relationship between ( r a ) cosθ = cosθ − cosθ and Wa values, liquid surface tensions and also perfluoro alkyl wt.% content of the copolymer were also investigated. Furthermore, the CAH and oil repellency differences between the p(Zonyl-TM-ran-S) and p(Zonyl-TM-ran- MMA) thin copolymer films with similar Zonyl-TM contents were also compared within this work. An increase was found in CAH values with the increase of hydrocarbon liquid chain length and thus liquid surface tension. This is due to the increase in cohesion interactions between liquid molecules and resulted in a decrease in adhesion interactions between the solid surface and the liquid drop.

Amphiphilic graft copolymers from end-functionalized starches: synthesis, characterization, thin film preparation, and small molecule loading.

End-functionalized macromolecular starch reagents, prepared by reductive amination, were grafted onto a urethane-linked polyester-based backbone using copper-catalyzed azide-alkyne cycloaddition (CuAAC) chemistry to produce novel amphiphilic hybrid graft copolymers. These copolymers represent the first examples of materials where the pendant chains derived from starch biopolymers have been incorporated into a host polymer by a grafting-to approach. The graft copolymers were prepared in good yields (63-90%) with high grafting efficiencies (66-98%). Rigorous quantitative spectroscopic analyses of both the macromolecular building blocks and the final graft copolymers provide a comprehensive analytical toolbox for deciphering the reaction chemistry. Due to the modular nature of both the urethane-linked polyester synthesis and the postpolymerization modification, the starch content of these novel hybrid graft copolymers was easily tuned from 28-53% (w/w). The uptake of two low molecular weight guest molecules into the hybrid polymer thin films was also studied. It was found that binding of 1-naphthol and pterostilbene correlated linearly with amount of starch present in the hybrid polymer. The newly synthesized graft copolymers were highly processable and thermally stable, therefore, opening up significant opportunities in film and coating applications. These results represent a proof-of-concept system for not only the construction of starch-containing copolymers, but also the loading of these novel polymeric materials with active agents.

Preparation and characterization of sulfonated poly(arylene ether ketone) copolymers with pendant sulfoalkyl groups as proton exchange membranes

A series of novel sulfonated poly(arylene ether ketone) (SPAEK) copolymers with pendant sulfoalkyl groups are prepared via nucleophilic polycondensation reactions. The sulfonate content of the SPAEK copolymers can be controlled easily by adjusting the ratio of the sulfonated and unsulfonated monomer feeds. The structures of the synthesized sulfonated copolymers are confirmed by 1H NMR and Fourier transform infrared spectra. The microstructures of the membranes are investigated by transmission electron microscopy. Mechanical properties, thermal and oxidative stabilities, water uptake, swelling ratio, proton conductivity, and methanol permeability of the membranes are systematically investigated. The results demonstrated that the membranes have good performance. The proton conductivities of the side-chain-type SPAEK-100 membrane reach 0.051 and 0.152 S cm−1 at 25 and 120 °C, respectively. The methanol permeabilities of the side-chain-type SPAEK membranes are in the range of 0.12 × 10−7–3.55 × 10−7 m2 s−1, which is lower than that of the Nafion 117 membrane, i.e., 23.8 × 10−7 m2 s−1. A higher relative selectivity than that of Nafion 117 is also observed. These results indicate that there is a great potential for side-chain-type SPAEK membranes to be used in proton exchange membrane fuel cell applications.

Tuning Gelation Time and Morphology of Injectable Hydrogels Using Ketone–Hydrazide Cross-Linking

Injectable, covalently in situ forming hydrogels based on poly(N-isopropylacrylamide) have been designed on the basis of mixing hydrazide-functionalized nucleophilic precursor polymers with electrophilic precursor polymers functionalized with a combination of ketone (slow reacting) and aldehyde (fast reacting) functional groups. By tuning the ratio of aldehyde:ketone functional groups as well as the total number of ketone groups in the electrophilic precursor polymer, largely independent control over hydrogel properties including gelation time (from seconds to hours), degradation kinetics (from hours to months), optical transmission (from 1 to 85%), and mechanics (over nearly 1 order of magnitude) can be achieved. In addition, ketone-functionalized precursor polymers exhibit improved cytocompatibility at even extremely high concentrations relative to polymers functionalized with aldehyde groups, even at 4-fold higher functional group densities. Overall, increasing the ketone content of the precursor copolymers can result in in situ-gellable hydrogels with improved transparency and biocompatibility and equivalent mechanics and stimuli-responsiveness while only modestly sacrificing the speed of gel formation.

Superhydrophobic perfluoropolymer surfaces having heterogeneous roughness created by dip-coating from solutions containing a nonsolvent

Superhydrophobic and oleophobic rough copolymer surfaces containing micro- and nano-hierarchical ball-like islands having diameters between 100nm and 7μm were formed using styrene-perfluoromethacrylate random copolymers which were dip-coated on glass slides from THF and MEK mixture containing methanol as nonsolvent. These copolymers were synthesized in a CO2-expanded monomer medium at 250bar pressure and 80°C. The sizes of the micro-islands can be controlled by varying the copolymer composition; and the degree of phase separation by adjusting the solvent/non-solvent ratio. Flat and lotus-like hierarchical surfaces of the copolymers were characterized using contact angle measurements and SEM. The increase in the perfluoromethacrylate content of the flat copolymers resulted in a decrease of the total surface free energy of the flat copolymer surfaces from 18.3 down to 14.2mJ/m2. The increase in the methanol non-solvent fraction resulted in decrease of the micro-island diameter from 7μm down to 100nm and the water contact angle increased from 117° up to 160° and hexadecane from 65° up to 90°.

Elastic/adhesive double-layered PLA-PEG multiblock copolymer membranes for postoperative adhesion prevention

Tissue adhesions cause severe and life-threatening conditions, including pain, infertility, and heart defects. The purpose of this study is to develop an anti-adhesion membrane that sticks onto the injured tissues or organs in order to avoid the suturing of the membrane which may lead to the unnecessary tissue adhesion. We previously developed poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) multiblock copolymers as soft, water absorbable, and quickly degradable biomaterials. The copolymer with the highest PEG content adsorbs body fluid in vivo and sticks to the tissues. In the present study thin film and nanofiber mat were prepared from the copolymer and evaluated in vitro and in vivo. The hydrophilicity and the degradation rate increased with the increased PEG content of the multiblock copolymers. The copolymer with PEG content of 88% (LE(m)-88) was quickly swollen, become viscous, and rapidly collapsed in PBS, which was suitable feature for adhesion prevention material without suturing. Various double layered membranes with different characteristics were evaluated in vivo by applying onto the cecum scrubbed with abrasive paper, and onto the heart surface after pericardium removal. LE(m)-88 was swollen with tissue fluid and had a hydrogel-like nature. LE(m)-88 film/LE(m)-32 film double layered membrane was found to be the most effective in preventing tissue adhesion in cecum model. This excellent performance was confirmed in the rat heart adhesion model. In both models, the LE(m)-32 support film was detached from the site of application, which leads to the healing without adhesion.

Zinc-Containing Block Copolymer as a Precursor for thein SituFormation of Nano ZnO and PMMA/ZnO Nanocomposites

We report on the synthesis of highly transparent and UV-absorbing PMMA/ZnO nanocomposites prepared by hydrolysis of a ZnO precursor, the A-b-(AB) diblock copolymer, poly(methyl methacrylate)-block-poly(methyl methacrylate-co-(zinc methacrylate acetate)), PMMA-b-P(MMA-co-ZnMAAc), synthesized by RAFT polymerization. The zinc content of the block copolymers was in the range from 3 to 13 wt %. The PMMA block provides inherent compatibility with the PMMA matrix, whereas the second block, P(MMA-co-ZnMAAc) with zinc ions, acts as a polymeric precursor for the formation of ZnO nanoparticles. The amphiphilic block copolymer self-organizes in THF and THF/H2O in ordered nanostructures, thereby influencing the nanoparticle formation during the hydrolysis of the precursor block copolymer with KOH in a solvent mixture THF/H2O. The ZnO nanoparticles were rod-shaped with lengths up to 80 nm and a diameter of 14 nm and were redispersible in THF. Dispersions in THF and thin films of PMMA/ZnO nanocomposite exhibit excellent...

Nanoaggregates of Biodegradable Amphiphilic Random Polycations for Delivering Water-Insoluble Drugs

Cationic amphiphilic random copolyesters were obtained by copolymerization of 5-Z-amino-δ-valerolactone and ε-caprolactone. The amino content of the final copolymers was controlled by the polymerization feed ratio and was in the range 10 to 100%. Copolymers solubility and aggregation behavior was assessed by conductometric and zeta potential analyses. A critical aggregation concentration of ca. 0.05% (w/v) was found for all water-soluble copolymers that formed nanoaggregates. Two populations were found to be present in equilibrium with hydrodynamic diameters in the range of 30-50 and 100-250 nm. The capacity to use the amphiphilic and cationic character of the nanoaggregates to encapsulate highly hydrophobic compounds was further investigated. Finally, copolymers hemo- and cytocompatibility were evaluated by hemagglutination, hemolysis, and cells proliferation tests. The results showed that the proposed cationic amphiphilic random copolyesters are biocompatible.

The effect of molecular weight, compositions and lectin type on the properties of hyperbranched glycopolymers as non-viral gene delivery systems

The architectures of gene delivery vectors, in addition to their molecular weights and compositions, can play a critical role in DNA condensation and hence on their gene expression. In general, branched polymers are superior gene delivery vectors as compared to their linear analogs. This study reports the efficacy of cationic hyperbranched glycopolymers for DNA condensation and gene expression. Hyperbranched glycopolymers of varying molecular weights and compositions are synthesized via reversible addition fragmentation chain transfer (RAFT) process and are further explored for their gene expression in vitro. Galactose-based hyperbranched polymers are compared to glucose-derived hyperbranched polymers for their cellular uptake, toxicity and gene expression. It is found that molecular weight of hyperbranched polymers, and carbohydrate content of copolymers are critical factors in determining the gene expression as well as in imparting the specificity to these novel gene delivery vectors. The galactose-based hyperbranched glycopolymer of ∼30 kDa or lower show improved gene expression at varying polymer/plasmid ratios. The incubation of hyperbranched polyplexes in the presence of serum protein show the presence of stable particles and gene expression of these hyperbranched polyplexes is unaffected in the presence of serum proteins. Furthermore, the cellular uptake and gene expression are studied in two different cell lines in the presence of lectins. It is found that polyplexes-lectin conjugates show enhanced cellular uptake in vitro, however their gene expression is cell line and lectin type dependent.