Influence Of Copolymer Composition Research Articles

Rationalizing the Composition Dependence of Glass Transition Temperatures in Amorphous Polymer/POSS Composites.

We report that the fractions of "bonded" or "unbonded" monomers at a filler interface dictate the composition dependence of the glass transition temperatures (Tg) of polyhedral oligomeric silsesquioxane (POSS)-containing nanocomposites. Tg is arguably the single most important material property; however, predicting Tg in nanocomposites is often challenging because of confounding interfacial effects. To this end, we design a model nanocomposite to systematically study Tg of nanocomposites by leveraging the "all-interfacial" nature of ultrasmall POSS fillers loaded into random copolymers of styrene and 2-vinylpyridine (2VP). The amine-functionalized POSS forms hydrogen bonds only with 2VP, which behaves as a "bonded" monomer. The influence of copolymer composition and POSS loading on the Tg of this model composite is successfully explained by a Fox equation framework. This model also captures the Tg increase of other POSS-based polymer composites and potentially directs the future design of nanocomposite materials with tailored Tg.

PH- and thermosensitive copolymers of 4-acryloylmorpholine and 2-dialkylaminoethyl methacrylates and silver-containing nanocomposites based on these copolymers

Luminescent-labeled copolymers of 4-acryloylmorpholine and 2-dialkylaminoethyl methacrylates (2-dimethylaminoethyl methacrylate and 2-diethylaminoethyl methacrylate) of varied compositions and molecular masses were synthesized. Polarized luminescence method was used to study relaxation properties of the polymers in diluted aqueous solutions. The influence of copolymer composition, temperature, pH, ionic strength of solutions on structural and dynamic characteristics of the copolymers in solution was established. The obtained copolymers were used to synthesize silver nanoparticles with an average radius of 7–8 nm. Interaction between the luminescent-labeled copolymers and Ag+ ions was studied. It was demonstrated that reduction of Ag+ by the copolymers and formation of Ag° is accompanied by decrease in mobility of polymer chains due to adsorption of macromolecules on the surface of Ag° nanoparticles and formation of a stabilizing shell.

The Influence of Copolymer Composition on PLGA/nHA Scaffolds' Cytotoxicity and In Vitro Degradation.

The influence of copolymer composition on Poly(Lactide-co-Glycolide)/nanohydroxyapatite (PLGA/nHA) composite scaffolds is studied in the context of bone tissue engineering and regenerative medicine. The composite scaffolds are fabricated by thermally-induced phase separation and the effect of bioactive nanoparticles on their in vitro degradation in phosphate-buffered solution at 37 °C is analyzed over eight weeks. The indirect cytotoxicity evaluation of the samples followed an adaptation of the ISO 10993-5 standard test method. Based on the measurement of their molecular weight, molar mass, pH, water absorption and dimensions, the porous scaffolds of PLGA with a lower lactide/glycolide (LA/GA) molar ratio degraded faster due to their higher hydrophilicity. All of the samples without and with HA are not cytotoxic, demonstrating their potential for tissue engineering applications.

Crystallization Behavior of Poly(p-dioxanone-co-glycolide) Copolymers

Poly(p-dioxanone-co-glycolide) (PDG) copolymers with high proportion of p-dioxanone (pDO) were synthesized by ring-opening polymerization of pDO and glycolide (GA) with stannous octoate-dodecanol as the initiator. The cooling crystallization and isothermal crystallization of PDG were studied by DSC and X-ray. The influence of copolymer composition on the crystallization behavior was discussed. With the increase of GA in the copolymer, the crystallinity of PDG was decreased firstly and then increased, but crystallization heat and crystallization speeds were weakened. The results provided guidance for determining copolymerization parameters and melt spinning of PDG.

Influence of PVP/VA copolymer composition on drug–polymer solubility

In this study, the influence of copolymer composition on drug–polymer solubility was investigated. The solubility of the model drug celecoxib (CCX) in various polyvinylpyrrolidone/vinyl acetate (PVP/VA) copolymer compositions (70/30, 60/40, 50/50 and 30/70w/w) and the pure homopolymers polyvinylpyrrolidone (PVP) and polyvinyl acetate (PVA) was predicted at 25°C using a thermal analysis method based on the recrystallization of a supersaturated amorphous dispersion (recrystallization method). These solubilities were compared with a prediction based on the solubility of CCX in the liquid monomeric precursors of PVP/VA, N-vinylpyrrolidone (NVP) and vinyl acetate (VA), using the Flory–Huggins lattice theory (liquid monomer solubility approach).The solubilities predicted from the liquid monomer solubility approach increased linearly with increasing VP/VA ratio from 0.03–0.60w/w. Even though the solubilities predicted from the recrystallization method also increased with increasing VP/VA ratio from 0.02–0.40w/w, the predicted solubility seemed to approach a plateau at high VP/VA ratios.Increasing positive deviations from the Gordon–Taylor equation with increasing VP/VA ratio indicated strong interactions between CCX and the VP repeat unit, which was in accordance with the relatively high solubilities predicted using both methods.As the solubility plateau may be a consequence of steric hindrance caused by the size differences between CCX and the VP repeat units, it is likely that a CCX molecule interacting with a VP repeat unit hinders another CCX molecule from binding to the neighboring repeat units in the polymer chain.Therefore, it is possible that replacing these neighboring hygroscopic VP repeat units with hydrophobic VA repeat units, could increase the physical stability of an amorphous solid dispersion without compromising the drug–polymer solubility. This knowledge could be used advantageously in future development of amorphous drug delivery systems as copolymers could be customized to provide optimal drug–polymer solubility and physical stability.

Influence of copolymer composition on the phase behavior of solid dispersions.

The incorporation of poorly soluble active pharmaceutical ingredients (APIs) into excipients (e.g., polymers) to formulate an amorphous solid dispersion is a promising strategy to improve the oral bioavailability of the API. The application of copolymer excipients allows access to combinations of different monomers and thus to the design of excipients to improve solid-dispersion properties. In this work, the thermodynamic phase behavior of solid dispersions was investigated as a function of the API, type of monomer, and copolymer composition. The glass-transition temperatures and API solubilities in the solid dispersions of naproxen and indomethacin in polyvinylpyrrolidone, polyvinyl acetate, and copolymers with different weight fractions of vinylpyrrolidone and vinyl actetate were investigated. It is shown that the thermodynamic phase behavior of API/copolymer solid dispersions is a function of monomer type and copolymer composition. This effect was also predicted by using the perturbed-chain statistical associating fluid theory (PC-SAFT). The glass-transition temperature of the solid dispersions was calculated with the Gordon-Taylor equation.

Toughening epoxy resins by modification with in situ polymerized acrylate copolymer composed of butyl acrylate and glycidyl methacrylate

Poly(butyl acrylate–glycidyl methacrylate) (PBG) was prepared by in situ polymerization of butyl acrylate (BA) and glycidyl methacrylate (GMA) and further used as a modifier to improve the comprehensive properties of the epoxy resin curing system. The modified resin system was based on diglycidyl ether of bisphenol, methyl tetrahydrophthalic anhydride, and tris(dimethylaminomethyl)phenol. The influence of copolymer composition on the mechanical properties, thermal performance, and phase behavior of the system was carefully examined. Results showed that the addition of PBG greatly improved the impact strength of the modified epoxy resin. When 15 wt% of the BA/GMA with a weight ratio composition of 7.5/7.5 was added to the epoxy, high-performance-modified epoxy resin was obtained.

Formation of Linear and Graft Block Copolymers at a Polymer/Polymer Interface: How Copolymer Brush and Microdomain Morphology Control Heterogeneous Reactions

Irreversible coupling between immiscible melts of two functionalized macromonomers A and B of different lengths resulting in the formation of a linear or graft block copolymer AB was modeled by dissipative particle dynamics. Recently (Macromolecules 2011, 44, 112), we investigated the mechanism of the instability caused by saturating an A/B interface with the copolymer product, which leads to a microdomain structure formation. The present simulations were focused on the influence of copolymer composition and architecture on the microstructure development and characteristics of different kinetic regimes. Nearly symmetric copolymers form bicontinuous microdomains facilitating mass transfer and resulting in the exponential coupling kinetics. Strongly asymmetric copolymers promote fragmentation of a minor phase into isolated domains hardly accessible for the remaining reactants so that the linear or even slower kinetics is observed. At an equal concentration of functional groups, grafting proceeds always slower than end-coupling since branched copolymers form less penetrable brushes at the interface than linear diblocks. The most effective screening is achieved with symmetric copolymers. Both end-coupling and grafting produce long-lived nonuniform microstructures, with the size and shape of domains monotonously changing along the distance from the initial A/B interface. In the interface vicinity, minor phase micelles can form ordered layers.

Structural characterization of nanoparticles from thermoresponsive poly(N-isopropylacrylamide)-DNA conjugate

Poly(N-isopropylacrylamide) (PNIPAAm) grafted with single-stranded (ss) DNA conjugate (PNIPAAm-g-DNA) self-assembles above its lower critical solution temperature to form colloidal particles. When the ssDNA within the particle hybridizes with its complementary DNA, the particles aggregate above a certain threshold of salt concentration with drastically increased turbidity in solution. Detailed structural information of the particle was obtained mainly by small-angle X-ray scattering. The influence of copolymer composition on the morphology of particle and non-crosslinking aggregation was examined. The particle consists of hydrophobic PNIPAAm core surrounded by hydrophilic DNA strands. The increase in DNA fraction brought about a significant decrease in core size, whereas the shell thickness little changed and corresponded to the length of DNA. A structural model with a sticky potential was applied to the analysis of particle aggregate. This analysis provided that the particles aggregate while the coronal layers interpenetrate each other. The interaction between the particles was quantified in terms of the sticky potential and showed a trend to be influenced by the particle size rather than the graft density of DNA strands on the particle.

Synthesis and characterization of a novel polymer electrolyte based on acrylonitrile/N-[4-(aminosulfonyl)phenyl]acrylamide copolymers

Acrylonitrile/N-[4-(aminosulfonyl)phenyl]acrylamide (AN/ASPAA) copolymers were synthesized and used as a host of lithium ion conducting electrolytes. The composition, molecular weight and molecular weight distribution of AN/ASPAA copolymers were determined, and the influence of copolymer composition on the glass temperature of AN/ASPAA copolymers and the ion conductivity of electrolytes were investigated. The molecular weights of AN/ASPAA copolymers were lower than those of AN and ASPAA homopolymers due to the cross-termination reaction. The glass temperatures of AN/ASPAA copolymers increased as the molar fraction of ASPAA units in copolymers increased. The lithium ion conductivities of the polymer electrolytes increased initially as the molar fraction of ASPAA units in copolymers increased, and a maximum conductivity was achieved when the molar fraction of ASPAA in the copolymer was 16.8%.

Radiation synthesis of poly[(dimethylaminoethyl methacrylate)-co-(ethyleneglycol dimethacrylate)] hydrogels and its application as a carrier for anticancer delivery

The use of hydrogels as carriers for anticancer delivery has been a subject of significant recent research. In our recent work, we have shown that diffusion-controlled delivery of flutamide from hydrogels containing poly (dimethylaminoethyl methacrylate (DMAEMA)/ethyleneglycol dimethacrylate (EGDMA)) can be possible and controlled by the three-dimensional structure. Hydrogels based essentially on dimethylaminoethyl methacrylate and different ratios of ethyleneglycol dimethacrylate monomers were synthesized using gamma radiation copolymerization. The influence of copolymer composition and pH value of the surrounding medium on swelling behavior into the glassy polymer were discussed. The results showed that the ratio of EGDMA in the comonomer feeding solution has a great effect on the gel fraction and water content in the final hydrogel. In this regard, it was observed that the increase of EGDMA ratio decreased these properties. The ability of the prepared copolymer to be used as drug carrier for anticancer drug-delivery system was estimated using flutamide as a model drug. In vitro drug-release studies in different buffer solutions show that the basic parameters affecting the drug release behavior of hydrogel are the pH of the solution and DMAEMA content of hydrogel.

EFFECT OF COMPOSITON ON THE VISCOELASTIC RELAXATION AND PHASE MORPHOLOGY OF LINEAR STYRENE-BUTADIENE-STYRENE TRIBLOCK COPOLYMERS

研究了不同组成的苯乙烯-丁二烯苯乙烯嵌段共聚物（SBS）的相形态与粘弹弛豫.用透射电子显微镜(TEM)表征了SBS的形态，结果显示，几种SBS均呈层状结构，随着苯乙烯含量的降低，聚苯乙烯（PS）相的尺寸稍有减小，而聚丁二烯（PB）相尺寸明显增大.用动态流变学方法考察了不同温度下SBS嵌段大分子的弛豫行为，结果表明，苯乙烯含量减少，PS相玻璃化转变和有序无序转变温度均降低；苯乙烯含量少的，在有序无序转变过程中呈现出高且宽的损耗峰，表明有序无序转变过程中能量的耗散主要由两相溶合时分子链间的内摩擦所决定，分子链越长，内摩擦越大，能量耗散越大.

Photodimerization of Coumarin Functionalized Poly(alkyl Acrylate) and Poly(alkyl Methacrylate) Random Copolymers: Influence of Copolymer Composition on Photocrosslinking

Coumarin‐containing poly(alkyl (meth)acrylates) were prepared via 70–80% esterification of hydroxy‐containing acrylic copolymers, then solution cast into thin films and photocrosslinked via the dimerization of coumarin derivatives with UVA light. The coumarin‐modified polymers crosslinked upon exposure and exhibited gel fractions between 74 and 99%. Coumarin dimerization efficiency increased with higher polymer mobility at the irradiation temperature. The effects of light intensity and irradiation time in photo‐dimerized systems followed the Bunsen‐Roscoe reciprocity law indicating that coumarin photodimerization depended only on dose. Thus, low intensities are overcome with longer times. This is an important advantage over photoinitiated free radical crosslinking which depends on irradiation intensity to the ½ power.

Effect of copolymer composition, temperature, and carbon dioxide fugacity on pure- and mixed-gas permeability in poly(ethylene glycol)-based materials: Free volume interpretation

Network copolymers, prepared by photopolymerizing poly(ethylene glycol) diacrylate (PEGDA: CH 2 CHCOO(CH 2CH 2O) 14OCCH CH 2) and poly(ethylene glycol) methyl ether acrylate (PEGMEA: CH 2 CHCO(OCH 2CH 2) 8OCH 3), have been studied for mixed-gas CO 2/H 2 and CO 2/CH 4 separations. Gas separation properties in the networks are sensitive to copolymer composition, temperature, and carbon dioxide fugacity in the feed. In conventional approaches, the effect of temperature can be described by the Arrhenius equation, while the influence of copolymer composition and fugacity can only be described empirically; the corresponding models require a large number of adjustable parameters. However, as shown here, the three factors influencing gas transport correlate well with free volume, and a simplified free volume model with only two adjustable parameters can satisfactorily describe the effects of copolymer composition, temperature, and CO 2 fugacity on pure- and mixed-gas transport properties. Copolymer composition and temperature can be directly related to the fractional free volume, while CO 2 fugacity of the feed can be correlated with free volume via the glass transition temperature of the polymer–gas mixture, which is computed using Chow's model.

Adsorption and controlled release of Chlortetracycline HCl by using multifunctional polymeric hydrogels

Adsorption and controlled release of Chlortetracycline HCl to and from multifunctional polymeric materials (HEMA/MAA) hydrogels were investigated. P(HEMA/MAA) hydrogels were synthesized by gamma radiation-induced copolymerization of 2-hydroxyethylmethacrylate (HEMA) and methacrylic acid (MAA) in aqueous solution. The influence of copolymer composition and pH value of the surrounding medium on the type of water diffusion into the glassy polymer were discussed. Drug, Chlortetracycline HCl containing hydrogels, with different drug concentration to polymer ratios, was loaded by direct adsorption method. The influence of MAA content in the gel on the adsorption capacities of hydrogel was studied. Chlortetracycline HCl adsorption capacity of hydrogels was found to increase from 8 to 138 mg Chlortetracycline HCl per gram dry gel with increasing amount of MAA in the gel system and drug concentration. The effect of pH on the releasing behavior of Chlortetracycline HCl from gel matrix was investigated. In vitro drug release studies in different buffer solutions show that the basic parameters affecting the drug release behavior of hydrogel are the pH of the solution and MAA content of hydrogel.

Hydrophobic modification of high molar mass polyglycidol to thermosensitive polymers

The results concerning a new class of thermosensitive polymers based on modified poly(2,3-epoxypropanol-1) – the polyglycidol are presented. Thermo-responsive water-soluble poly(glycidol-co-ethyl glycidyl carbamate)s were obtained by the hydrophobic modification of hydroxyl groups of the polyglycidol chain with ethyl isocyanate. The cloud points of the synthesized poly(glycidol-co-ethyl glycidyl carbamate)s were measured by UV–VIS and the hydrodynamic behaviour of the polymer chains near the transition temperature was characterized by dynamic light scattering. The influence of copolymer composition and polymer concentration on the cloud point was investigated. The cloud point was easy controlled in a range from 22 to 81 °C by change of the degree of modification. The effect of the surfactant sodium n-dodecylsulphate (SDS) and inorganic salt (NaCl) on the temperature response of synthesized copolymer was also examined.

Alkoxysilane Functional Acrylic Latexes: Influence of Copolymer Composition on Self‐Curing Behavior and Film Properties

AbstractReactive latexes based on acrylic polymers with trimethoxysilyl groups in the side chain were prepared by semi‐continuous emulsion copolymerization. The properties of the latex film related to the polymer network structure and their evolution upon thermal curing were studied as a function of the content of the reactive comonomer, trimethoxysilylpropyl methacrylate (TSPMA), ranging between 8 and 25 wt‐%. In particular, the sensitivity to both organic solvent (chloroform) and water and the thermomechanical properties were investigated by swelling experiments and dynamic‐mechanical analysis (DMA). The results are interpreted in terms of a transition from uniform to microheterogeneous crosslinking regime, possibly as the result of formation of polyorganosilsesquioxane‐like (POSS) crosslinking domains at higher TSPMA content.

Influence of Copolymer Composition on the Structure of Conducting Poly(aniline-co-o-phenylenediamine)

This study covers the synthesis of polymers of aniline, o-phenylenediamine, and their copolymers by chemical oxidation in HCl medium. The composition of the copolymers was changed by varying the monomer feed ratio. For examining the effect of composition on copolymer structure and properties, the copolymers were characterized by elemental analysis, FTIR, UV-visible spectra, and thermal analysis. The electrical conductivity of the compressed pellets was measured by the two-probe method. Magnetic studies shows that the polyaniline is paramagnetic in nature, which shows the presence of three unpaired electrons per chain unit, while the poly(o-phenylenediamine) and copolymers are diamagnetic and are found to contain no unpaired electrons. The copolymer exhibits excellent solubility in DMF. It was interesting to find that 20% o-phenylenediamine-containing copolymer exhibits good solubility by retaining a conductivity similar to polyaniline. The spectroscopic analysis, solubility test, and electrical conductivity suggest that aniline and o-phenylenediamine units are distributed along the copolymer chain and the properties of copolymers can be modified by varying the monomer composition in copolymerization reactions. TG thermogram shows three-stage decomposition of the copolymer. Rapid decomposition starts after 400°C. The observed weight loss of samples was less than 17% at 225°C, showing good thermal stability of copolymers.

Radiation synthesis of interpolymer polyelectrolyte complex and its application as a carrier for colon-specific drug delivery system

Novel pH-sensitive interpolymer polyelectrolyte complex was synthesized by gamma radiation-induced copolymerization of acrylic acid (AAc) and dimethyl aminoethyl methacrylate (DMAEMA). pH-dependent swelling showed different phase transitions depending on the copolymer composition and also showed the interpolymer polyelectrolyte complex formation at pH values ranged from pH 3 to pH 4. FT-IR and TGA was employed to study the complex formation. The influence of copolymer composition and pH value of the surrounding medium on the type of water diffusion in the glassy polymer was discussed. The ability of the prepared copolymer to be used as drug carrier for colon-specific drug delivery system was estimated using ketoprofen as a model drug.

Influence of copolymer composition on the transport properties of conducting copolymers: poly(aniline-co-o-anisidine)

The effect of different compositions of monomers on the transport properties of copolymers by various techniques such as optical, electrical and magnetic has been investigated and compared with the homopolymers. The UV-visible absorption spectra show a hypsochromic shift with an increase in the o-anisidine content in copolymers indicating a decrease in the extent for conjugation (i.e. an increase in the bandgap). From temperature dependence of electrical conductivity the transport parameters such as charge localization length and average hopping distance are calculated and also the effect of the monomeric composition on the coherence length has been discussed. The magnetic studies show the paramagnetic and diamagnetic nature of homopolymers and copolymers. The X-ray diffraction pattern indicates that the copolymers are of amorphous nature.