Effect Of Copolymer Composition Research Articles

Towards high-performance polysulfone membrane: The role of PSF-b-PEG copolymer additive

Polysulfone (PSF) membranes were prepared by nonsolvent-induced phase separation (NIPS) method using PSF-b-PEG copolymer as pore formation additive. The effects of copolymer composition, hydrophilic chain length and copolymer dosage on membrane morphologies, permeability, stability and biocompatibility were systematically discussed in order to determine the role of the additive. The results suggest that the copolymer composition and dosage play an important role in pore formation. The increase of PEG content in the copolymer results in larger pore size and narrower pore size distribution. The modified membranes show average surface pore sizes in the range of 11.4–15.2 nm, which increase by 14–52% compared to that of the pristine PSF membrane. With increase of copolymer dosage, the pore size increases first and then decreases. The hydrophilic chain length has no significant influence on the pore size and size distribution. The results of pure water flux and rejection agree with the variation of pore size. With increasing the copolymer dosage, the static adsorption of protein and platelet to the membrane is suppressed and thus the antifouling ability is improved. The PSF-b-PEG copolymer outperforms the common water soluble additive (i.e. PVP) in terms of the better pore forming ability and membrane stability, implying that the PSF-b-PEG copolymer would be an alternative to PVP in membrane preparation.

Effect of polyester/PEG mixed micelles composition on preparation of multicompartment nanoparticles: Influence of crystallinity on morphology

In this study, the overall morphology of a mixture of two types of pentablock copolymers was studied. Poly(butylene adipate)-polyethylene glycol (PBA/PEG) and poly(diethyleneglycol adipate)-polyethylene glycol (PDEGA/PEG) dendritic copolymers have been prepared by condensation polymerization. PDEGA-PEG and PBA-PEG mixed micelles were synthesized via nanoprecipitation method and the effect of copolymer composition on morphology, stability, drug loading, in vitro release, and mucoadhesion property of nanoparticles was evaluated. It was found that by changing the composition of two pentablocks in the binary mixed micelles, their morphology and their inner structure can be definitely tuned from uniform mixed micelle to multicompartment one. In vitro mucoadhesion and drug release profile of the nanoparticles were investigated and it was observed that mixing of the two copolymers with specific characteristics can provide a useful situation for preparation of nanocarriers with unique properties for practical applications.

Smart nanoparticles based on pullulan-g-poly(N-isopropylacrylamide) for controlled delivery of indomethacin

Double hydrophilic thermo-responsive pullulan-g-poly(N-isopropylacrylamide) (P-g-pNIPAM) copolymers with two different molecular weight of thermosensitive grafts were synthesized and used for preparation of indomethacin-loaded nanoparticles by dialysis and nanoprecipitation method. The polymers form aggregates in aqueous solution at a concentration of 10g/L, above their critical aggregation concentration (3.36g/L) and below the lower critical solution temperature (LCST). After indomethacin loading, nanoparticles with compact and uniform structure were formed below the LCST. The effects of copolymer composition, concentration, and the feed polymer/drug ratio on the particle size, drug loading content (DLC) and entrapment efficiency (EE) were investigated. DLC increased with drug feeding, reaching a maximum value of 40% at the ratios of 1/1. Smaller particles (145nm) with narrower size distribution were obtained from polymer with a higher molecular weight of pNIPAM grafts.FT-IR and 1H NMR spectra proved that the main driven force for the aggregation was the hydrogen bonding between indomethacin and the pNIPAM side chains of copolymer.The indomethacin release rate from nanoparticles was influenced by temperature, because of the dissociation of the hydrogen bonds at high temperatures, the degree of drug loading, and the pH of the release media.

The effect of copolymer composition on the batch foaming dynamics of styrene/methylmethacrylate copolymers

In this work, styrene/methyl methacrylate (St/MMA) copolymer particles were synthesized by suspension polymerization process with different copolymer compositions to study the visual batch foaming dynamics. The visualization system consisted of the self-sealing observation cell equipped to the pressure and temperature controller. The synthesized copolymer particles were impregnated by n-pentane, followed by recording of particle expansion. The cell structure of foams was studied by scanning electron microscopy. The effect of different foaming conditions on the expansion behavior of copolymers was examined. It was concluded that sorption pressure and temperature have contradictory effects on the foaming ratio of the synthesized copolymers at lower and higher sorption pressures, and the results were confirmed with the foams’ cell structure. Furthermore, it was shown that, at different temperatures and pressures, the expansion behavior change dramatically with increasing of MMA content in the copolymer.

PH- and Metal Ion- Sensitive Hydrogels based on N-[2-(dimethylaminoethyl)acrylamide

Smart hydrogels are promising materials for actuators and sensors, as they can respond to small changes in their environment with a large property change. Hydrogels can respond to a variety of stimuli, for example temperature, pH, metal ions, etc. In this article, the synthesis and characterization of polyampholyte hydrogels based on open chain ligands showing pH and metal ion sensitivity are described. Copolymer and terpolymer gels using different mixtures of monomers i.e., N-[2-(dimethylaminoethyl)acrylamide] (DMAEAAm), N,N-dimethylacrylamide (DMAAm), acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulphonic acid (AMPS), have been synthesized. The effect of copolymer composition, i.e., the ratio and amount of ionic monomers and the degree of crosslinking on the swelling characteristics, was evaluated as a function of pH. On this basis, metal ion sensitivity measurements were performed at selected pH values. The metal ion sensitivity was measured by varying the concentration of Cu2+, Zn2+ and Ag+ ions under acidic pH conditions.

Effects of copolymer composition, film thickness, and solvent vapor annealing time on dewetting of ultrathin block copolymer films

Effects of copolymer composition, film thickness, and solvent vapor annealing time on dewetting of spin-coated polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films (<20nm thick) were mainly investigated by atomic force microscopy. Surface chemical analysis of the ultrathin films annealed for different times were performed using X-ray photoelectron spectroscopy and contact angle measurement. With the annealing of acetone vapor, dewetting of the films with different thicknesses occur via the spinodal dewetting and the nucleation and growth mechanisms, respectively. The PS-b-PMMA films rupture into droplets which first coalesce into large ones to reduce the surface free energy. Then the large droplets rupture into small ones to increase the contact area between PMMA blocks and acetone molecules resulting from ultimate migration of PMMA blocks to droplet surface, which is a novel dewetting process observed in spin-coated films for the first time.

Investigations on Preparation and Characterization of Certain Copolyesters

In this paper, we report on the synthesis and characterization of high molecular weight copolyesters from Terephthalic acid, 1, 4 butane diol and Succinic acid /Sebacic acid through a two step process of melt polycondensation using titanium tetra butoxide as catalyst. The synthesized aromatic-aliphatic random copolyesters were characterized by means of FTIR, 1H NMR,13C NMR, Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Gel Permeation Chromatography (GPC) and Scanning Electron Microscope (SEM) studies. The effect of copolymer composition on the physical and thermal properties as well as degradation test was investigated. The degradation test was carried out in alkali medium. The phase behaviour of the polymers was studied by differential scanning calorimetry and optical polarising microscopy. The results revealed that the newly synthesized copolyesters exhibited degradability and thermotropic liquid crystalline behaviour with nematic texture which was revealed by optical polarising microscopy. The Novelty of this work is that the glass transition temperature and melting temperature are above the room temperature for the synthesized polymers. This shows the good thermal stability which results in early processing of liquid crystalline materials.

Toward efficient water/oil separation material: Effect of copolymer composition on pH‐responsive wettability and separation performance

Interest in functional soft matter with stimuli‐responsive wettability has increasingly intensified in recent years. From the chemical product engineering viewpoint, this study aims to fabricate reversible pH‐responsive polymeric surfaces with controllable wettability using [poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate)‐block‐ poly(acrylic acid) (PHFBMA‐b‐PAA)] block copolymers. To attain this aim, three block copolymers with different PAA segment lengths were synthesized for the first time through Cu(0)‐mediated reversible‐deactivation radical polymerization and hydrolysis reaction. pH‐induced controllable wettability was achieved by spin‐coating the resulting block copolymers onto silicon wafers. Results showed that the pH‐responsive wetting behavior was introduced by incorporating the PAA block, and that the responsiveness of as‐fabricated surfaces was greatly influenced by PAA content. All three evolutions of water contact angle with pH shared a similar inflection point at pH 5.25. Furthermore, on the basis of the wetting properties and mechanism understanding, the application of copolymer coated meshes in layered water/oil separation was exploited. Given their superhydrophilicity and underwater superoleophobicity, PHFBMA70‐b‐PAA148 and PHFBMA70‐b‐PAA211 coated stainless steel meshes (SSMs) can efficiently separate water from different mixtures of organic solvent and water with high flux. However, considering long‐term use, the PHFBMA70‐b‐PAA148 coated SSM with good stability may be the best copolymer for water/oil separation. Therefore, a coordination of structure, composition, and functionality was necessary to enable practical applications of the functional materials. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1758–1771, 2016

캘콘기를 가지는 메타크릴레이트 고분자: 모노머 반응성비와 열적 광학적 성질

A new methacrylate copolymer that includes chalcone as a side group, poly(4-methacryloyloxyphenyl-4'-methoxystyryl ketone-co-styrene) was synthesized by free radical copolymerization. FTIR and <TEX>$^1H$</TEX> NMR spectroscopic techniques were used to characterize the homopolymers and copolymers. The copolymerizations were carried out to high conversions. Copolymer compositions were established by <TEX>$^1H$</TEX> NMR spectra analysis. The monomer reactivity ratios for copolymer system were determined by the linearized Kelen <TEX>$T{\ddot{u}}d{\ddot{o}}s$</TEX>, and Extended Kelen <TEX>$T{\ddot{u}}d{\ddot{o}}s$</TEX> methods and a non-linear least squares method. The molecular weights and polydispersity index of copolymers were measured by using the gel permeation chromatography (GPC). The effect of copolymer compositions on their thermal behavior were studied by differential scanning calorimetry and thermogravimetric analysis methods. The optical properties of the resulting copolymer were also investigated.

PH and Thermo Sensitive Superabsorbent Poly (N-Hydroxymethylacrylamide-co-Itaconic Acid) Hydrogels: Synthesis, Characterization and Kinetic Studies

In this study, itaconic acid (IA) was co-polymerized with N-hydroxymethylacrylamide (NHMAA) by free radical solution polymerization to prepare pH and thermo sensitive superabsorbent hydrogels. The polymerization process was carried out at 25°C by using ammonium persulfate (APS) and N,N,N’,N’-tetramethylethylenediamine (TMEDA) as initiating system and ethyleneglycoldimethacrylate (EGDMA) as a crosslinking agent. The effects of copolymer composition, crosslinking agent concentration, pH and temperature on swelling capacity and kinetic parameters were investigated. The copolymer hydrogels were characterized by using swelling studies and FT-IR analyses. The equilibrium degree of swelling of hydrogels was found to increase as pH value of the swelling solution varied from 2 to 12 and temperature from 45 to 25°C. The dynamic swelling studies have showed that, the diffusion exponent(n) and the diffusion coefficient(k) both increase with increasing content of itaconic acid.

High energy density and breakdown strength from β and γ phases in poly(vinylidene fluoride-co-bromotrifluoroethylene) copolymers.

Poly(vinylidene fluoride) PVDF-based copolymers represent the state of the art dielectric polymers for high energy density capacitors. Past work on these copolymers has been done with limited emphasis on the effects of copolymer composition and with a limited range of defect monomers, focusing primarily on the commercially available poly(vinylidene fluoride-co-chlorotrifluoroethylene), P(VDF-CTFE), and poly(vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), and the processing thereof. To expand on this area of research, copolymers of VDF and bromotrifluoroethylene (BTFE) were synthesized examining the composition range where uniaxial stretching was possible. It is found that P(VDF-BTFE) copolymers with small BTFE contents (< 2 mol %) stabilize the γ phase, compared to P(VDF-CTFE)s and P(VDF-HFP)s that are largely α phase in composition. Furthermore, different from P(VDF-CTFE)s and P(VDF-HFP)s, whose energy storage capabilities depend on the reversibility of the α to β phases transformation, high discharged energy densities (i.e., 20.8 J/cm(3) at 716 MV/m) are also achievable through the β and γ phases in P(VDF-BTFE)s without significantly reducing crystallinity and breakdown strength. This study demonstrates new avenues to the development of high energy density ferroelectric copolymers via manipulation of the γ phase through variation of the structure and content of comonomers.

Copolymerization of cyclohexene-3-yl methyl methacrylate with styrene: synthesis, characterization, monomer reactivity ratios, and thermal properties

A methacrylate monomer, cyclohexene-3-yl methyl methacrylate (CHMA) was synthesized by reaction of 3-cyclohexene-1-methanol with methacryloyl chloride in the presence of triethylamine at 0–5 °C. The homopolymer of CHMA and its copolymer with styrene (St) were prepared by free radical polymerization. The Fourier transform infrared (FT-IR), 1H NMR, and 13C NMR spectroscopic techniques were used to characterize the homopolymers and copolymers. 1H NMR spectra were used to determine the compositions of the copolymers. Linearization methods such as Kelen–Tüdös, Extended Kelen–Tüdös, and a non-linear least squares method were all used to determine the reactivity ratios of the monomers. The effect of copolymer compositions on their thermal behavior was studied by differential thermal analysis and thermogravimetric analysis methods.

Co-Assembly of A–B Diblock Copolymers with B′-type Nanoparticles in Thin Films: Effect of Copolymer Composition and Nanoparticle Shape

The coassembly of A–B diblock copolymers with B′-type nanoparticles (i.e., nanoparticles that are slightly incompatible with the B domain) leads to hierarchical structures, where the block copolymer phase separates first and the nanoparticles create close-packed arrays within the B domains due to a slower, secondary phase separation process. Here we report the results of a comprehensive study, which focused on two aspects: the influence of the nanoparticle shape (spherical vs rod-like) and the effect of the volume composition of the blocks. Three polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) copolymers featuring similar molecular weights but differing in PS volume fraction were mixed with spherical and rod-shaped poly(ethylene oxide)- (PEO-) capped CdS nanoparticles at different filling fractions and cast as thin films. Our results highlight the mutual influence between the block copolymer and the nanoparticles on the resulting morphology, demonstrating the ability to control the film morphology by the filling fraction of the nanoparticles and their tendency to localize at the film surface, and by confinement-induced nanoparticle aggregation. Most importantly, the results reveal the influence of the nanoparticle shape on the structure of the film.

Light scattering of ideal random copolymers in bulk

Copolymerization is a useful way of modifying the physical properties of a material to meet specific needs, but it can result in a significant light scattering loss due to dielectric fluctuations in the material. Ideal random copolymers are known to be more transparent; however, the light-scattering properties of such copolymers in bulk have not been fully studied. In this paper, two representative ideal random copolymers were synthesized: methyl methacrylate (MMA)/benzyl methacrylate (BzMA) and MMA/2,2,2-trifluoroethyl methacrylate (TFEMA). The effects of copolymer composition and polymerization temperature on the light-scattering properties were investigated. Polarized light scattering (VV) in copolymers was more sensitive to the polymerization temperature. Higher temperatures were necessary to homogenize the dielectric fluctuations and minimize excess light scattering. However, once the heterogeneous structures vanished, the copolymer bulk exhibited low scattering losses, which are comparable with homopolymers, over the entire range of copolymer compositions.

Novel pentablock copolymer (PLA–PCL–PEG–PCL–PLA)-based nanoparticles for controlled drug delivery: effect of copolymer compositions on the crystallinity of copolymers and in vitro drug release profile from nanoparticles

The purpose of this investigation was to design novel pentablock copolymers (polylatide-polycaprolactone-polyethylene glycol- polycaprolactone-polylatide) (PLA-PCL-PEG-PCL-PLA) to prepare nanoparticle formulations which provide continuous delivery of steroids over a longer duration with minimal burst effect. Another purpose was to evaluate the effect of poly (L-lactide) (PLLA) or poly (D, L-lactide) (PDLLA) incorporation on crystallinity of pentablock copolymers and in vitro release profile of triamcinolone acetonide (selected as model drug) from nanoparticles. PLA-PCL-PEG-PCL-PLA copolymers with different block ratio of PCL/PLA segment were synthesized. Release of triamcinolone acetonide from nanoparticles was significantly affected by crystallinity of the copolymers. Burst release of triamcinolone acetonide from nanoparticles was significantly minimized with incorporation of proper ratio of PDLLA in the existing triblock (PCL-PEG-PCL) copolymer. Moreover, pentablock copolymer based nanoparticles exhibited continuous release of triamcinolone acetonide. Pentablock copolymer based nanoparticles can be utilized to achieve continuous near zero-order delivery of corticosteroids from nanoparticles without any burst effect.

Release of dexamethasone from poly(N‐vinyl pyrrolidone‐co‐n‐hexyl methacrylate) copolymers of controlled hydrophilicity

AbstractA copolymer system with controlled hydrophilicity has been prepared through copolymerization technique and its capability as controlled drug release carrier is investigated. The effect of copolymer composition on water uptake, thermal properties, and morphology is reported. The water uptake increases with increasing N‐vinyl pyrrolidone content and diffusion of water molecules appears to be non‐Fickian. Dexamethasone has been selected as model drug and its controlled release from selected water stable copolymers follows for more than 1 month. Initial burst release of more than 50% occurs in 7 days. The remaining drug is released in a sustained way upto 37 days. Initial 10 h drug release pattern involves first‐order kinetics (NH73) and zero‐order kinetics (NH55), whereas initial 60% drug release mechanism appears to be non‐Fickian for NH73 (n = 0.71) and Case II transport (n = 1.24) for NH55. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

Antifouling ultrafiltration membranes made from PAN-b-PEG copolymers: Effect of copolymer composition and PEG chain length

Antifouling ultrafiltration membranes were prepared by polyacrylonitrile-block-polyethylene glycol (PAN-b-PEG) copolymers through immersion precipitation phase inversion method. The effect of copolymer composition and PEG chain length on the structure and property of the block copolymer membranes were investigated. Compared with PAN membranes, PAN-b-PEG copolymer membranes possessed excellent hydrophilic surface due to the enrichment of PEG segments, which was confirmed by X-ray photoelectronic spectroscopy (XPS) and contact angle measurements. SEM images showed these PAN-b-PEG copolymer membranes had a typical asymmetric structure similar with PAN membranes, but the thinner skin layer was helpful for the membrane resistance reduction. The PAN-b-PEG copolymer membranes exhibited better antifouling ability for BSA than PAN membranes. The BSA absorption amount on the copolymer membrane could reduce 45% than that on the PAN membrane, and its irreversible fouling extent could lower 7 times. The hydrophilicity and antifouling ability of the copolymer membranes increased with increasing PEG content in the copolymer. While the chain length of PEG had little effect on the hydrophilicity and antifouling ability of the copolymer membrane.

Micellar Behavior of Polystyrene-Poly(Ethylene Oxide) Diblock Copolymers in Aqueous Media: Effect of Copolymer Composition, Temperature, Salt, and Surfactants

Formation and structure of micelles from two amphiphilic polystyrene-block-poly(ethylene oxide) (PS-PEO) diblock copolymers (PS mol.wt. 1000; PEO mol.wt. 3000 and 5000) were examined by surface tension, viscosity, steady state fluorescence, dynamic light scattering (DLS), small angle neutron scattering (SANS), and cryo-transmission electron microscopy (cryo-TEM). The critical micelle concentration (CMC) of the copolymers in aqueous solution was ca. 0.05%; micelle hydrodynamic diameter was 30–35 nm with a narrow size distribution. SANS studies show that the copolymers form ellipsoidal micelles with semi major axis ∼23 nm and semi minor axis ∼8 nm. No significant change in the structure was found with temperature and presence of salt. The copolymer micelles interaction with the ionic surfactants sodium dodecyl sulphate (SDS) and dodecyltrimethylammonium bromide (DTAB) was also examined by DLS and SANS.

Influence of chain microstructure on ethylene–norbornene copolymer film properties

AbstractThe effects of copolymer composition, copolymer composition distribution, and polar α‐olefin incorporation on transparency, refractive index, and hydrophilicity of resultant ethylene–norbornene copolymer films were investigated. It has been found that the transparency is mainly determined by the copolymer composition distribution. The samples having uniform compositions gave better transparency. However, the copolymer composition distribution had little effect on refractive index. The refractive index increased linearly with increasing norbornene content. Furthermore, the incorporation of polar α‐olefin with long carbon chain improved refractive index and hydrophilicity of the films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Copolymer networks from carboxyl‐containing polyaryletherketone and diglycidyl ether of bisphenol‐A: Preparation and properties

AbstractThis article presents a new type of epoxy‐toughening system, in which high‐Tg polyaryletherketone (PEK‐L) containing one carboxyl group per repeating unit was utilized to randomly copolymerize with epoxy resin (DGEBA) to form crosslinking network. Compared to the neat epoxy resin, the PEK‐L/DGEBA copolymers showed simultaneous enhancement in flexural strains at break by 282%, GIC value by 193%, and flexural strength by 14%. The reason was attributed to the uniform three‐dimensional copolymer network interweaved by PEK‐L and DGEBA segments through strong covalent bonds. The copolymerization process were monitored and examined by FTIR spectra. The effect of copolymer composition on the thermal and mechanical properties as well as toughening mechanism were also investigated and discussed in detail. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010