Effect Of Copolymer Composition Research Articles

The effects of chlorotrifluoroethylene (CTFE) units on the dielectric and energy storage properties of P(VDF‐CTFE)

AbstractPolyvinylidene fluoride‐based ferroelectric polymers are favoured in the field of advanced high‐energy‐storage dielectric capacitors due to their strong spontaneous polarisation and high dielectric constant (εr). It has been confirmed that the ferroelectric behaviour and energy storage performance can be regulated by copolymerising polyvinylidene fluoride with bulky monomers such as chlorotrifluoroethylene, and hexafluoropropylene. Past research based on these copolymers mostly focused on the preparation of composites, yet with limited discussion on the effect of copolymer composition. In this work, a series of P(VDF‐CTFE) films with different chlorotrifluoroethylene contents were fabricated through a solution‐casting method. The introduction of bulky chlorotrifluoroethylene units can tune the polymer crystal structure and crystallinity, alter the state of polymer chains and the response of dipoles to electric fields, and lead to dramatic changes in dielectric properties, breakdown strength (Eb), and energy storage density (Ue). As a result, the copolymer with a chlorotrifluoroethylene content of 15 wt% obtained the best overall performance, and the Ue reached 16.73 J/cm3 at 650 kV/mm. This work provides a basis for the optimisation of the properties of polyvinylidene fluoride‐based ferroelectric polymers and the development of high Ue dielectric.

Chiral Copolymers of (R)-N-(1-Phenyl-Ethyl) Methacrylamide (R-NPEMAM) and 2-Hydroxy Ethyl Methacrylate (HEMA): Investigation of Physico- Chemical Behavior, Thermal Properties and Degradation Kinetics

In this paper, we report the microstructural investigation and influence of H-bonding on the thermal behavior e.g., glass transition (Tg) and thermal degradation of chiral copolymers of (R)- N-(1-phenyl-ethyl) methacrylamide (R-NPEMAM) and 2-hydroxy ethyl methacrylate (HEMA). The Tg increases with the increase of chiral unit content in the copolymers and then attains optimum at around 25 mole % of chiral content. Thereafter it decreases with the increase of chiral content. The effect of copolymer composition and secondary interaction associated with the Hbonding on the thermal properties of these copolymers was also studied. Secondary interaction, specifically H-bonding has been interpreted using FTIR analysis. The copolymers thermally degrade in three stages. The first and third stages of degradation are associated with the chiral comonomer (R-NPEMAM) whereas the second stage indicates the degradation due to HEMA unit present in the copolymer chain. The activation energies for these degradations of the copolymers have been evaluated using Flynn-Wall and Kissinger method.

Development of Azo Dye Immobilized Poly (Glycidyl Methacrylate-Co-Methyl Methacrylate) Polymers Composites as Novel Adsorbents for Water Treatment Applications: Methylene Blue-Polymers Composites.

Methylene blue azo dye (MB) immobilized onto Poly (glycidyl methacrylate-Co-methyl methacrylate), (PGMA-co-PMMA), and sulphonated Poly (glycidyl methacrylate-Co-methyl methacrylate), (SPGMA-co-PMMA), polymers composites have been developed as novel adsorbents for water treatment applications. The effect of copolymer composition and sulphonation on the MB content has been studied. Maximum MB content was correlated to the Polyglycidyl methacrylate content for both native and sulphonated copolymers. Furthermore, the effect of the adsorption conditions on the MB content was studied. Sulfonated Poly (glycidyl methacrylate; SPGMA) was the most efficient formed composite with the highest MB content. The developed composites' chemical structure and morphology were characterized using characterization tools such as particle size, FTIR, TGA, and SEM analyses. The developed MB-SPGMA composite adsorbent (27 mg/g), for the first time, was tested for the removal of Cr (VI) ions and Mn (VII) metal ions from dichromate and permanganate contaminated waters under mild adsorption conditions, opening a new field of multiuse of the same adsorbent in the removal of more than one contaminants.

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.

Effects of Copolymer Composition on Phase Transition Behavior and Mobility of Mesogenic Group for Side-Chain Liquid Crystalline-Amorphous Random Copolymers

Effects of Copolymer Composition on Phase Transition Behavior and Mobility of Mesogenic Group for Side-Chain Liquid Crystalline-Amorphous Random Copolymers

PAN-Based Triblock Copolymers Tailor-Made by Reversible Addition–Fragmentation Chain Transfer Polymerization for High-Performance Quasi-Solid State Dye-Sensitized Solar Cells

For efficient polymer gel electrolytes (PGEs) in quasi-solid-state dye-sensitized solar cells (QSS-DSSCs), six ABA triblock copolymers based on (poly(acrylonitrile-co-N-(isobutoxymethyl)acrylamide)-block-poly(ethylene glycol)-poly(acrylonitrile-co-N-(isobuto-xymethyl)acrylamide)) (P(AN-co-BMAAm)-b-PEG-b-P(AN-co-BMAAm)) with various copolymer compositions and molecular weights, coded as SGT-605, SGT-606, SGT-608, SGT-609, SGT-611, and SGT-612, have been synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization using PEG-functionalized macro-RAFT agents. The effects of copolymer compositions and molecular weights in P(AN-co-BMAAm)-b-PEG-b-P(AN-co-BMAAm) triblock copolymers were investigated in terms of electrochemical properties and photovoltaic performance as PGEs. The ionic conductivity was increased with N-(isobutoxymethyl)acrylamide (BMAAm) composition of these triblock copolymers, which is attributed to the availability of free iodide ions by complex formation among acrylamide groups with Li+ ions. However, polymer gel electrolytes with high molecular weights enhance ionic conductivity due to the lower amount of polymers required for the gel formation. Thus, the photovoltaic performances of PGE-based QSS-DSSCs improved along with the increase in the molecular weight of the triblock copolymer. The addition of 7 wt % TiO2 nanofiller into PGEs produced a higher ionic conductivity and diffusion of I3– than the corresponding PGEs. The resulting power conversion efficiency (PCE) of QSS-DSSCs using SGT-612/TiO2 composite PGEs under simulated 1-sun condition was 9.83% (Voc, 792.8 mV; Jsc, 16.65 mA/cm2; FF, 74.52%), which was higher than that of liquid electrolyte DSSCs (PCE 9.53%; Voc, 743.8 mV; Jsc, 17.16 mA/cm2; FF, 74.64%). The long-term device stability of PGE-based QSS-DSSCs was better than the liquid-state DSSCs.

Effect of Copolymer Composition on Thermodynamic Interactions in Blends Containing a Diene–Olefin Copolymer and a Polyolefin

Thermodynamic interactions in binary blends of a copolymer containing diene and olefin repeat units and a polyolefin were explored, through measurements of the effective binary Flory–Huggins intera...

Dewetting behavior of self-assembled films of polystyrene-b-poly(methyl methacrylate) induced by solvent vapor annealing

We once studied the dewetting behaviors of spin-coated and Langmuir−Blodgett (LB) films of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) induced by solvent vapor annealing (SVA), and revealed the different contact degrees between hydrophilic PMMA blocks and the substrate in the above two kinds of films. In this work, the dewetting behavior of self-assembled films of PS-b-PMMA induced by SVA was studied for the first time. Effects of copolymer composition, solution concentration, and SVA time were systematically considered. With the increase of SVA time, continuous flat self-assembled films undergo complicated progresses including the formation of bicontinuous or holed structures, the formation of droplets, and the periodic increase and decrease of droplet sizes. The periodic evolutions of droplet sizes in the self-assembled films are similar to those in our previous LB films but different from their single evolutions in the spin-coated films. It indicates that the former two kinds of films have good contact degrees between PMMA blocks and the substrate. Furthermore, the contact degrees in the self-assembled films are better than those in the LB films. In our current minds, the contact degrees are mainly related to the length of hydrophilic blocks and their parallel/vertical segment ratio to the substrate.

Scalable Synthesis of Amphiphilic Copolymers for CO2- and Water-Selective Membranes: Effect of Copolymer Composition and Chain Length

Dehumidification is a critical energy-intensive and crucial process for several industries (e.g., air conditioning and gas dehydration). Polymeric membranes with high water vapor permeability and s...

Pendant dual-sulfonated poly(arylene ether ketone) multi-block copolymer membranes for enhanced proton conductivity at reduced water swelling

The proton exchange membranes are synthesized from poly(arylene ether ketone) (PAEK) multi-block copolymers with and without sulfonated groups. The hydrophilic PAEK block is dual - sulfonated at the pendant site to enhance the proton conductivity of the membrane, while the hydrophobic block length is enlarged to reduce its swelling (increase dimensional stability) associated with water accommodation. The chemical structures of the synthesized oligomers and copolymers are identified using 1H and 19F NMR, ATR-FTIR, and GPC. The ion cluster dimension of the membrane is analyzed by SAXS. The effect of copolymer composition on the membrane properties is investigated measuring the proton conductivity, water uptake, swelling ratio, and cell performance along with the thermal, mechanical, and oxidative stability. The prepared membranes exhibit lower swelling ratio but higher proton conductivity than Nafion115 membrane. Specifically, B.PAEK25-SDPA shows superior cell performance to Nafion115.

Trimethoxysilyl end-capped hyperbranched polyglycidol/polycaprolactone copolymers for cell delivery and tissue repair: synthesis, characterisation and aqueous solution properties

New PCL-HBPG/SiHBPG triblock copolymers composed of a polycaprolactone (PCL) core with two outer blocks of trimethoxysilyl end-capped hyperbranched polyglycidol (HBPG/SiHBPG), of varying molecular weight, have been successfully synthesised and characterised. The effect of copolymer composition and structure upon the crystallization, melting, thermal degradation and aqueous solution behaviour were investigated at various temperatures. In aqueous solution, at concentrations above their corresponding critical aggregation concentration the PCL-HBPG/SiHBPG copolymers readily self-assemble into large multicore structures composed of PCL domains and corona consisting of HBPG/SiHBPG branches. The multicore structures were stabilized by numerous hydrogen-bonds from the HBPG moieties as well as via formation of siloxane crosslinks (i.e. SiOSi bonds). As the formation of the siloxane linkages is irreversible the PCL-HBPG/SiHBPG-based particles will be covalently crosslinked at higher concentrations in vivo and form injectable gels scaffolds that will be biocompatible and capable of invoking cell attachment and differentiation without the need for exogenous biological stimuli.

Effect of copolymer composition on particle morphology and release behavior in vitro using progesterone

This study was aimed at improving dissolution rate and sustained release of progesterone by varying copolymer composition and polymer: drug ratio of PLGA. Drug-loaded particles were prepared using electrohydrodynamic atomization. The effects of polymer: drug ratio and copolymer composition on particle properties and in vitro drug-release profile were investigated. The physical form of the generated particles was determined via X-ray powder diffraction (XRPD) and Fourier transform infrared spectroscopy (FTIR). Drug release in vitro was found to be dependent on copolymer composition, where the release rate increased with decreased lactide content of PLGA. Particles produced with solutions of copolymer (75:25) had elongated shapes. In general, the obtained results indicated that the prepared microparticles were ideal carriers for oral administration of progesterone offering great potential to improve the dissolution rate of drugs that suffer from low aqueous solubility.

The effect of copolymer composition, gas content, and temperature on the bubbles nucleation and growth of styrene–methyl methacrylate copolymer/n-pentane foaming process

The foaming process involves three important steps: nucleation, bubble growth, and stability. In the present work, the foaming dynamics of styrene–methyl methacrylate (St-MMA) copolymer/ n-pentane batch foaming system was studied at nonpressurized condition using rapid temperature increasing method. Synthesized copolymers with different compositions were characterized by proton nuclear magnetic resonance analysis and rheological measurements. An in situ foaming observation apparatus was designed, and the foaming dynamics (nucleation and bubble growth behavior) was studied. Dissolved n-pentane contents in all synthesized copolymer compositions at saturation temperatures, near their glass transition temperatures, were determined. The effects of foaming temperature, copolymer composition, and n-pentane content on the foaming dynamics of St-MMA copolymer/ n-pentane system were investigated. The foaming results revealed that the nucleation rate was increased with the increasing foaming temperature, while two other aforementioned parameters were kept constant. The nucleation and bubble growth rate were decreased with increasing MMA units in copolymer composition and increased with dissolved n-pentane content increment in copolymer matrix.

Poly(vinylphosphonic acid-co-acrylic acid) hydrogels: The effect of copolymer composition on osteoblast adhesion and proliferation.

There is a clinical need for a synthetic bone graft substitute that can be used at sites of surgical intervention to promote bone regeneration. Poly(vinylphosphonic acid‐co‐acrylic acid) (PVPA‐co‐AA) has recently been identified as a potential candidate for use in bone tissue scaffolds. It is hypothesized that PVPA‐co‐AA can bind to divalent calcium ions on bone mineral surfaces to control matrix mineralization and promote bone formation. In this study, hydrogels of PVPA‐co‐AA have been produced and the effect of copolymer composition on the structure and properties of the gels was investigated. It was found that an increase in VPA content led to the production of hydrogels with high porosities and greater swelling capacities. Consequently, improved cell adhesion and proliferation was observed on these hydrogels, as well as superior cell spreading morphologies. Furthermore, whereas poly(acrylic acid) gels were shown to be relatively brittle, an increase in VPA content created more flexible hydrogels that can be more easily molded into bone defect sites. Therefore, this work demonstrates that the mechanical and cell adhesion properties of PVPA‐co‐AA hydrogels can be tuned for the specific application by altering the copolymer composition. © 2017 The Authors Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 255–264, 2018.

Polyacrylamide–b-copolypeptide hybrid copolymer as pH-responsive carrier for delivery of paclitaxel: Effects of copolymer composition on nanomicelles properties, loading efficiency and hemocompatibility

In the current study, a series of pH-responsive di/tri-block copolymers of poly N-(2-hydroxypropyl) methacrylamide–b-poly histidine/poly leucine (pHPMA-pHis/pLeu) were developed through sequential RAFT and ring-opening polymerization. Chemical structure of the synthesized copolymers was studied by FT-IR and 1H NMR spectroscopy and their molecular weight was characterized by size exclusion chromatography (SEC). The study of dynamic light scattering (DLS) revealed that copolymers could self-assemble into nanomicelles with particle size (PS) of 96–233nm which increased in acidic media. Higher fpLeu and fpLeu/fpHis led to significantly smaller PS and CMC values, respectively. Higher CMC values, together with zeta potential reversal at acidic pH and having buffering activity at pH range of about 6–8 were indications of protonation of imidazole groups of histidine residues and pH-sensitiveness of hybrid copolymers. Atomic force microscopy also proved the DLS data. Hemocompatibility assay demonstrated that while only tri-block copolymers caused hemolysis at neutral pH, all copolymers caused significant hemolysis at low concentrations at pH 5.2 and pLeu had opposite effects on hemolysis percent at different pH values. Paclitaxel was efficiently loaded in nanomicelles with highest loading efficiency (LE) of 75% which was influenced by the composition of the copolypeptide block. PTX-loaded micelles of tri-block copolymer 5-5-3 showed accelerated PTX release in endosomal pH. In conclusion, the optimum designed copolymer can be considered as a good pH-sensitive candidate for drug delivery to solid tumors.

Synthesis of Star-Comb Double Crystalline Diblock Copolymer of Poly(ε-caprolactone)-block-poly(l-lactide): Effect of Chain Topology on Crystallization Behavior

A series of highly branched star-comb poly(e-caprolactone)-block-poly(l-lactide) (scPCL-b-PLLA) are successfully achieved using star-shaped hydroxylated polybutadiene as the macroinitiator by a simple “grafting from” strategy. The ration of each segment can be controlled by the feed ratio of comonomers. These star-comb double crystalline copolymers are well-defined and expected to illustrate the influences of the polymer chain topology by comparing with their counterparts in linear-shaped, star-shaped, and linear-comb shape. The crystallization behaviors of PCL-b-PLLA copolymers with different architectures are investigated systematically by means of wide-angle X-ray diffraction, differential scanning calorimetry, and polarized optical microscopy analysis. It is shown that the comb branched architectures promote the crystallization behavior of each constituent significantly. Both crystallinity and melting temperature greatly raise from linear to comb-shaped copolymers. Compared to linear-comb topology, the star-comb shape presents some steric hindrance of the graft points, which decrease the crystallinity of scPCL-b-PLLA. Effects of copolymer composition and chain topology on the crystallization are studied and discussed.

Nanostructure development in polystyrene‐b‐polybutadiene‐b‐poly(methyl methacrylate) (SBM) thin films by atomic force microscopy: Effect of copolymer composition and solvent

Surface morphology development for SBM triblock copolymer thin films has been studied by atomic force microscopy. The effect of copolymer composition and solvent on the final morphology has been investigated. Obtained results indicated that depending on the block ratio (symmetric or asymmetric with minority middle block) and solvent, lamellar, hexagonal, cylindrical, or spheres in lamellae (ls)‐type morphologies can be achieved at film surfaces. The influence of the interaction parameters among blocks and solvents and cohesive energy values of block pairs on the final morphology has been proved. POLYM. ENG. SCI., 58:422–429, 2018. © 2017 Society of Plastics Engineers

Filled copolymer membranes for pervaporative dehydration of ethanol-water mixture

Abstract Mixed matrix type filled copolymer membranes were prepared by in situ incorporation of nano sized sodium montmorilonite (NaMMT) clay into the matrix of the copolymer during emulsion radical polymerization of acrylonitrile (AN) and acrylic acid (AA) at three different molar ratios of AN: AA of 5:1, 10:1 and 15:1. The structure of the copolymer and filler-polymer compatibility was characterized by FTIR, XRD, SEM and mechanical properties. These membranes were used for dehydration of ethyl alcohol in the concentration range of 76–99.5 wt% alcohol including azeotropic composition (95.6 wt% of alcohol in water at atmospheric pressure). The effect of copolymer composition, wt% of nano clay and feed concentration on sorption, flux, separation factor, membrane permeability and intrinsic membrane selectivity were studied. The effect of feed temperature on solvent flux and membrane permeability were also studied. The interactive effects of the synthesis and process parameters were optimized by Box-Behnken design (BBD) of response surface methodology (RSM). The long term stability of the membranes was also evaluated by studying flux and selectivity over a long period of time.

Hydrogels based on copolymers of 2‐hydroxyethylmethacrylate and 2‐hydroxyethylacrylate as a delivery system for proteins: Interactions with lysozyme

ABSTRACTHydrogels have attracted considerable attention due to numerous applications, in particular as contact lenses and carriers for sustained drug delivery. The aim of the present work is to characterize the interactions of copolymer hydrogels consisted of 2‐hydroxyethylmethacrylate (HEMA) and 2‐hydroxyethylacrylate (HEA) with a small protein (lysozyme) and to assess the potential applications of these hydrogels as a drug delivery system for sustained release of protein‐based therapeutics. Physicochemical properties of protein‐loaded hydrogels, as well as lysozyme in vitro loading and release and the conformation of the protein released from hydrogels were studied. The effect of copolymer composition on the protein deposition on hydrogels and protein aggregation in the presence of hydrogels was also assessed. The results show that introduction of HEA into the copolymeric hydrogels enhances their suitability as a delivery system for proteins. Copolymerisation of HEMA and HEA allows controlling the physicochemical properties of hydrogels and the protein release rate. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44768.

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.