Effect Of Copolymer Composition Research Articles

Palladium Nanoparticles by Electrospinning from Poly(acrylonitrile-co-acrylic acid)−PdCl2 Solutions. Relations between Preparation Conditions, Particle Size, and Catalytic Activity

Catalytic palladium (Pd) nanoparticles on electrospun copolymers of acrylonitrile and acrylic acid (PAN-AA) mats were produced via reduction of PdCl2 with hydrazine. Fiber mats were electrospun from homogeneous solutions of PAN-AA and PdCl2 in dimethylformamide (DMF). Pd cations were reduced to Pd metals when fiber mats were treated in an aqueous hydrazine solution at room temperature. Pd atoms nucleate and form small crystallites whose sizes were estimated from the peak broadening of X-ray diffraction peaks. Two to four crystallites adhere together and form agglomerates. Agglomerate sizes and fiber diameters were determined by scanning and transmission electron microscopy. Spherical Pd nanoparticles were dispersed homogeneously on the electrospun nanofibers. The effects of copolymer composition and amount of PdCl2 on particle size were investigated. Pd particle size mainly depends on the amount of acrylic acid functional groups and PdCl2 concentration in the spinning solution. Increasing acrylic acid concentration on polymer chains leads to larger Pd nanoparticles. In addition, Pd particle size becomes larger with increasing PdCl2 concentration in the spinning solution. Hence, it is possible to tune the number density and the size of metal nanoparticles. The catalytic activity of the Pd nanoparticles in electrospun mats was determined by selective hydrogenation of dehydrolinalool (3,7-dimethyloct-6-ene-1-yne-3-ol, DHL) in toluene at 90 °C. Electrospun fibers with Pd particles have 4.5 times higher catalytic activity than the current Pd/Al2O3 catalyst.

Effect of Copolymer Composition on the Dynamic Mechanical and Thermal Behaviour of Butyl Acrylate‐Acrylonitrile Copolymers

AbstractThis article reports data on the dynamic mechanical and thermal behaviour of butyl acrylate‐acrylonitrile copolymers and their variation with copolymer composition. The copolymers were prepared by emulsion polymerisation techniques, using potassium peroxodisulfate initiator at 80 ± 2 °C. Films were prepared from the latex by casting and analysed by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). For copolymer with 0.7 weight fraction of butyl acrylate the dynamic mechanical behaviour was identical to the synthetic rubber NBR (acrylonitrile‐butadiene rubber), such that the storage modulus shows a rapid decay with increasing temperature. The damping characteristics, as indicated by the tan δ value, increased as the weight fraction of butyl acrylate in the copolymer increased. The dynamic mechanical data has been analysed with the WLF‐Equation to study the time‐temperature relationship. The dynamic mechanical properties and glass transition data point to the formation of a copolymer, whose properties vary with acrylonitrile content. Thermogravimetric analysis revealed that weight loss occurring at a particular temperature decreases, along with the decomposition rate, with increase in acrylonitrile content. The activation energy (Ea) for the decomposition was calculated using the Coats & Redfern equation. When temperatures for 10% copolymer decomposition are compared from TGA data, the acrylonitrile rich copolymer starts decomposing at a lower temperature, but the rate of decomposition is slower and yields higher char yields.Effect of copolymer composition on the variation of tan δ (max) at a measuring frequency of 1 Hz.magnified imageEffect of copolymer composition on the variation of tan δ (max) at a measuring frequency of 1 Hz.

A study of the radiation degradation of styrene/alkane and α‐methylstyrene/alkane copolymers

AbstractThe effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and α‐methylstyrene/alkane copolymers have been studied. The primary radical species formed on radiolysis of the copolymers at 77 K, and identified by ESR spectroscopy, are the same as those formed during radiolysis of the homopolymers. The yields of radicals for the copolymer are as predicted assuming that the cross‐section is proportional to the electron density of each component; however, there is some evidence of radical migration to aromatic groups at 77 K. Changes in molecular structure on irradiation were detected by using 13C NMR spectroscopy. Evidence of the consumption of terminal double bonds, and chain scission in α‐methylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross‐linking predominating in styrene/alkane copolymers, while in α‐methylstyrene/alkane copolymers chain scission was the major result of irradiation. Copyright © 2003 Society of Chemical Industry

Synthesis, characterization, and rheological studies of methacrylic acid–ethyl acrylate–diallyl phthalate copolymers

AbstractCopolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was performed by the emulsion polymerization technique in the presence of a mixture of ionic and nonionic emulsifiers, at 85°C, using potassium persulfate as initiator (0.16 wt % of monomer). The molar ratio of MAA : EA varied between 44 : 56 and 54 : 46 in the monomer feed. Copolymers of MAA and EA were synthesized by incorporating diallyl phthalate (DAP) with varying concentrations (0–1.7 mol % of total monomer) in the feed. A copolymer latex of MAA, EA, and DAP was also prepared by the variable feed process. The intrinsic viscosity and gel content were determined. Copolymers were characterized by IR and NMR spectroscopic techniques. The composition of copolymers was determined by 1H‐NMR spectra and sequential distribution from 13C{1H}‐NMR spectra. The pH of the copolymer emulsion varied between 3 and 10 by addition of aqueous ammonia (23% w/w) and its effect on Brookfield viscosity was studied. The effects of copolymer composition, crosslinking agent concentration in the feed, monomer feed process, polymer solid contents, and shear rate on Brookfield viscosity were studied at pH ∼ 8. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1430–1441, 2003

Effect of copolymer composition on the physicochemical characteristics, in vitro stability, and biodistribution of PLGA–mPEG nanoparticles

The physicochemical properties, the colloidal stability in vitro and the biodistribution properties in mice of different PLGA–mPEG nanoparticle compositions were investigated. The nanoparticles were prepared by a precipitation–solvent evaporation technique. The physical characteristics and the colloidal stability of the PLGA–mPEG nanoparticles were significantly influenced by the composition of the PLGA–mPEG copolymer used to prepare the nanoparticles. PLGA–mPEG nanoparticles prepared from copolymers having relatively high mPEG/PLGA ratios were smaller and less stable than those prepared from copolymers having relatively low mPEG/PLGA ratios. All PLGA–mPEG nanoparticle compositions exhibited prolonged residence in blood, compared to the conventional PLGA nanoparticles. The composition of the PLGA–mPEG copolymer affected significantly the blood residence time and the biodistribution of the PLGA–mPEG nanoparticles in liver, spleen and bones. The in vivo behavior of the different PLGA–mPEG nanoparticle compositions did not appear to correlate with their in vitro stability. Optimum mPEG/PLGA ratios appeared to exist leading to long blood circulation times of the PLGA–mPEG nanoparticles. This may be associated with the effects of the mPEG/PLGA ratio on the density of PEG on the surface of the nanoparticles and on the size of the nanoparticles.

Homopolimeryzacja metakrylanu 3-chloro-2-hydro-ksypropylu i jego kopolimeryzacja z metakrylanem metylu

Conditions of preparation of sombre homopolymers of 3-chloro2-hydroxypropyl methacrylate (CHPMA) and copolymers of CHPMA with methyl methacrylate (MMA), obtained by radical polymerization in 1,4-dioxane solution, have been determined. Results of the investigations of the effects of initial CHPMA concentration and polymerization time on the reaction course show that to obtain soluble products, concentration of CHPMA should be ≤ 5 vol.%. Chemical structures of homopolymers and copolymers obtained have been determined using the following methods: IR (Fig. 1), Raman spectroscopy (Fig. 2), 1 H NMR (Fig. 3) and 1 3 C NMR (Fig. 4). Microstructures of these products have been also determined: molar fractions of syndiotactic, heterotactic and isotactic triads and meso and racemic diads (Table 1). The experimental results evidence that MMa is more reactive comonomer. The effect of copolymer composition on its density and glass transition temperature was investigated. M n and M w /M n were determined by GPC method.

The Effect of Copolymer Composition on Surface Free‐Energy of Poly(2‐Hydroxyethyl Methacrylate–Crotonic Acid) Copolymers

Poly(2‐hydroxyethyl methacrylate–crotonic acid) P(HEMA/CrA) copolymers with varying compositions were prepared from ternary mixtures of 2‐hydroxyethyl methacrylate (HEMA)/crotonic acid (CrA)/water by using 60Co γ‐rays. The wetting forces were determined according to the Wilhelmy Plate Technique. Di‐iodomethane, ethylene glycol, and formamide were used as probe liquids. Lifshitz–van der Waals surface energy components, Lewis acid–base surface components, and total surface energies were calculated using van Oss et al. methodology. It was determined that Lifshitz–van der Waals component (γS LW) of the copolymers did not differ much from the copolymer composition. However, the electron‐donor surface free energy components (γS −) of the copolymers were decreased considerably with the increase of the CrA content of the copolymers, the surfaces of these copolymers were still found to have a basic character.

Biodegradable polyesters based on succinic acid

Two series of aliphatic polyesters based on succinic acid were synthesized by copolymerization with adipic acid for the first series of saturated polyesters, and with fumaric acid for the second series. Polyesters were prepared starting from the corresponding dimethyl esters and 1,4-butanediol by melt transesterification in the presence of a highly effective catalyst tetra-n-butyl-titanate, Ti(0Bu)4. The molecular structure and composition of the copolyesters was determined by 1H NMR spectroscopy. The effect of copolymer composition on the physical and thermal properties of these random polyesters were investigated using differential scanning calorimetry. The degree of crystallinity was determined by DSC and wide angle X-ray. The degrees of crystallinity of the saturated and unsaturated copolyesters were generally reduced with respect to poly(butylene succinate), PBS. The melting temperatures of the saturated polyesters were lower, while the melting temperatures of the unsaturated copolyesters were higher than the melting temperature of PBS. The biodegradability of the polyesters was investigated by enzymatic degradation tests. The enzymatic degradation tests were performed in a buffer solution with Candida cylindracea lipase and for the unsaturated polyesters with Rhizopus arrhizus lipase. The extent of biodegradation was quantified as the weight loss of polyester films. Also the surface of the polyester films after degradation was observed using optical microscopy. It could be concluded that the biodegradability depended strongly on the degree of crystallinity, but also on the flexibility of the chain backbone. The highest biodegradation was observed for copolyesters containing 50 mol.% of adipic acid units, and in the series of unsaturated polyesters for copolyesters containing 5 and 10 mol.% of fumarate units. Although the degree of crystallinity of the unsaturated polyesters decreased slightly with increasing unsaturation, the biodegradation was not enhanced suggesting that not only the chemical structure and molecular stiffness but also the morphology of the spherulites influenced the biodegradation properties.

Complexation Phenomena in pH-Responsive Copolymer Networks with Pendent Saccharides

Sugar-containing copolymer networks of poly(methacrylic acid-co-methacryloxyethyl glucoside) were prepared by free-radical photopolymerization. Incorporation of the MAA in the polymer networks rendered the networks complex forming, in response to the environmental pH change. Using ATR−FTIR spectroscopy, the polymer complexes were investigated in their hydrated state. It was observed that in acidic media hydrogen bonds formed due to the protonation of the carboxylic acid groups of the PMAA while in basic or neutral conditions electrostatic repulsion occurred between the ionized carboxylic acid groups. This complexation affected the macroscopic swelling properties. The effect of copolymer compositions on the network structure was investigated. Both hydrogen-bonding and electrostatic interactions increased with MAA content in the networks.

Thermogravimetric study of copolymers derived from p-dioxanone, l-lactide and poly (ethylene glycol)

Thermogravimetric (TG) and differential thermogravimetry (DTG) analysis of the block copolymers based on poly ( p-dioxanone) PPDO or poly ( l-lactide) PLLA or poly ( p-dioxanone-co- l-lactide) PDO/PLLA and diol-terminated poly(ethylene glycol) PEG segments is reported. The effect of copolymer composition on the thermal stability of the copolymer under nitrogen and air is discussed. For comparison, the degradation behaviours of the starting oligomers and their corresponding homopolymers were also studied. The results showed that under nitrogen copolymers exhibited two degradation steps that can be ascribed to the PPDO or PLLA or PDO/LLA and PEG segments, respectively. However, under air copolymers exhibited almost a single degradation step. Most of the copolymer samples showed higher stability in air than in nitrogen. All the copolymer samples in air as well as in nitrogen were eventually burnt almost completely.

Synthesis and characterization of methacrylic derivatives of 5-amino salicylic acid with pH-sensitive swelling properties

The purpose of this study is to develop novel colon-specific drug delivery systems with pH-sensitive swelling and drug release properties. Methacrylic-type polymeric prodrugs with different content levels of 5-amino salicylic acid (5-ASA) were synthesized by free radical copolymerization of metacrylic acid (MAA), polyethylene glycol monomethacrylate (PEGMA), and a methacrylic derivative of 5-ASA (methacryloyloxyethyl 5-amino salicylate [MOES]). The copolymers were characterized, and the drug content of the copolymers was determined. The effect of copolymer composition on the swelling behavior and hydrolytic degradation was studied in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.2). The swelling and hydrolytic behavior of the copolymers was dependent on the content of MAA groups and caused a decrease in gel swelling in SGF or an increase in gel swelling in SIF. Drug release studies showed that increasing content of MAA in the copolymer enhances the hydrolysis in SIF but has no effect in SGF. The results suggest that hydrogen-bonded complexes are formed between MAA and PEG pendant groups and that these pH-sensitive systems could be useful for preparation of a controlled-release formulation of 5-ASA.

Synthesis and characterization of methacrylic derivatives of 5-amino salicylic acid with pH-sensitive swelling properties.

The purpose of this study is to develop novel colon-specific drug delivery systems with pH-sensitive swelling and drug release properties. Methacrylic-type polymeric prodrugs with different content levels of 5-amino salicylic acid (5-ASA) were synthesized by free radical copolymerization of metacrylic acid (MAA), polyethylene glycol monomethacrylate (PEGMA), and a methacrylic derivative of 5-ASA (methacryloyloxyethyl 5-amino salicylate [MOES]). The copolymers were characterized, and the drug content of the copolymers was determined. The effect of copolymer composition on the swelling behavior and hydrolytic degradation was studied in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.2). The swelling and hydrolytic behavior of the copolymers was dependent on the content of MAA groups and caused a decrease in gel swelling in SGF or an increase in gel swelling in SIF. Drug release studies showed that increasing content of MAA in the copolymer enhances the hydrolysis in SIF but has no effect in SGF. The results suggest that hydrogen-bonded complexes are formed between MAA and PEG pendant groups and that these pH-sensitive systems could be useful for preparation of a controlled-release formulation of 5-ASA.

Blends of poly(hydroxypropyl methacrylate) with 4-vinyl-co-N-vinyl-2-pyrrolidone and with vinyltrimethylsilane-co-N-vinyl-2-pyrrolidone copolymers. The effect of copolymer composition on interpolymer compatibility

Blends of poly(hydroxypropyl methacrylate) with 4-vinyl-co-N-vinyl-2-pyrrolidone and with vinyltrimethylsilane-co-N-vinyl-2-pyrrolidone copolymers. The effect of copolymer composition on interpolymer compatibility

Effects of Copolymer Composition and Free Volume Change on the Miscibility of Poly(styrene-co-vinylphenol) with Poly(ε-caprolactone)

A series of poly(styrene-co-vinylphenol) (PSOH) copolymers were prepared and characterized. The miscibility and hydrogen bonding between the partially hydroxylated polystyrene with poly(- caprolactone) (PCL) blend were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The copolymers containing higher than 13 mol % vinylphenol were found to be fully miscible with PCL according to differential scanning calorimetry studies. Quantitative analyses on the fraction of hydrogen-bonded carbonyl groups in the solid state were made by FTIR spectroscopy, and good correlations between thermal behaviors and infrared results were observed. The critical vinylphenol content of 0.1 mol % in PSOH copolymer for the blend to be miscible was predicted from the Painter- Coleman association model and binary interaction model. The discrepancy between the experimental result and theoretical prediction is probably caused by significant free volume increase in this blend system, which is analyzed by the Kovacs' free volume theory. The free volume of the PSOH/PCL is increased which give a positive contribution in the Gibbs free energy. As a result, the polystyrene needs to incorporate more poly(vinylphenol) in PSOH copolymer in order to overcome the free energy increased caused by the free volume increase predicted by the Painter-Coleman association model and the binary interaction model.

Enzymatic hydrolysis of random copolypeptides consisting of N-hydroxypropy1- l-glutamine and l-leucine

Two component water soluble random copolypeptides consisting of N-hydroxypropyl- l-glutamine and l-leucine were prepared by carrying out aminolysis reactions with 3-amino-1-propanol (P) on starting copolymers (ML) consisting of γ-methyl- l-glutamate (M) and l-leucine. The effects of copolymer composition and sequential distributions, as well as molecular conformations, on the rate of degradation by bromelain were investigated in a PECF at pH 7.4 and 37.0°C to simulate in vivo polymer degradation. All the samples were found to be degraded by random chain fracture with bromelain. Further, the degradation data for these samples followed the Michaelis–Menten rate law, being of the first order in bromelain concentration. The nature of the side chains and the molecular conformations are important to the rate of degradation by bromelain in vitro and it was controlled by the comonomer composition as well as the sequential distribution of comonomers in the copolymer chains.

Poly(ethylene oxide)/poly(butylene terephthalate) segmented block copolymers: the effect of copolymer composition on physical properties and degradation behavior

In this study, the influence of copolymer composition on the physical properties and the degradation behavior of thermoplastic elastomers based on poly(ethylene oxide) (PEO) and poly(butylene terephthalate) (PBT) segments is investigated. These materials are intended to be used in medical applications where degradability of the implant is desired. PEOT/PBT copolymers are microphase separated and up to four thermal transitions are measured by differential scanning calorimetry. Phase separation in the system is enhanced by increasing the molecular weight of starting poly(ethylene glycol) (PEG) or by increasing the PBT content. The mechanical properties, swelling characteristics and degradation rates of the copolymers are influenced by the phase separation. By changing the PEOT/PBT composition, tensile strengths vary from 8 to 23 MPa and elongations at break from 500 to 1300%. Water uptake ranges from 4 to 210%. The in vitro degradation of PEOT/PBT copolymers occurs via hydrolysis and oxidation. In both cases, degradation is more rapid for copolymers with high contents of PEO. Deterioration of copolymer films takes place when the films are exposed to light in the absence of antioxidant. In preventing oxidation under daylight conditions, Irganox 1330 turned out to be a more efficient antioxidant for the copolymers than vitamin E.

Effect of copolymer composition on the miscibility of poly(styrene- co-acetoxystyrene) with phenolic resin

The miscibility behavior and specific interaction of phenolic/polystyrene- co-acetoxystyrene, (PS- co-PAS) blends by varying acetoxystyrene contents of the PS- co-PAS copolymer were investigated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). A miscibility window was found when the acetoxystyrene fraction in the copolymer is higher than 45 mol% in phenolic/PS- co-PAS=50/50 blend system. Painter–Coleman Association Model (PCAM) is able to predict the miscibility window at 150°C compared with our experimental results based on DSC analyses.

A wireless, remote query ammonia sensor

This paper presents a wireless, remote query ammonia sensor comprised of a free-standing magnetoelastic thick-film coated with a polymer, poly(acrylic acid-co-isooctylacrylate), that changes mass in response to atmospheric ammonia concentration. The mass of the polymer layer modulates the resonant frequency the ferromagnetic magnetoelastic substrate, hence by monitoring the frequency response of the sensor, atmospheric NH 3 concentration can be determined remotely, without the need for physical connections to the sensor or specific alignment requirements. The effect of copolymer composition, polymer film thickness, and relative humidity level (RH) on the sensitivity of the sensor were investigated. The sensor linearly tracks ammonia concentration below 0.8 vol.%, and tracks higher concentrations logarithmically; within the linear calibration range, a 0.02 vol.% change in NH 3 concentration can be detected.

Synthesis and characterization of biodegradable poly(butylene succinate- co-butylene adipate)s

A series of high molecular weight polyesters, poly(butylene succinate- co-butylene adipate)s was prepared from dimethyl succinate, dimethyl adipate and 1,4-butanediol by catalyzed transesterification in the melt. The structure, average molecular weights and physical properties of the resulting random aliphatic copolyesters were characterized by 1H NMR, solution viscosity, gel permeation chromatography, differential scanning calorimetry and X-ray analysis. The effect of copolymer composition on the physical and thermal properties, as well as enzymatic degradation was investigated. The enzymatic degradation was performed in a buffer solution with Candida cylindracea lipase at 30 °C. The highest enzymatic degradation rate was observed for the copolyester containing 50 mol.% butylene succinate units (PBAS-50). This copolyester has the lowest crystallinity and these results suggest that degree of crystallinity has a strong influence on the enzymatic degradation rate.

Effect of Copolymer Composition and Solvent Polarity on the Phase Behavior of Mixtures of Poly(ethylene-co-vinyl acetate) with Cyclopentane and Cyclopentene

The free radical polymerization of ethylene-based copolymers is typically performed in a single-phase region which requires that the operating pressure be held high enough to inhibit phase separation but low enough to make the process economically feasible. In this paper special attention is given to the change in phase behavior that results by the random incorporation of polar vinyl acetate groups in the backbone of a nonpolar polyethylene chain.