Copolymers Of Different Compositions Research Articles

Synthesis and Characterization of Thermoresponsive Chitosan-graft-poly(N-isopropylacrylamide) Copolymers.

Thermoresponsive chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) copolymers of different composition were synthesized by free-radical polymerization of chitosan (CS) and N-isopropylacrylamide (NIPAAm) in aqueous solution using potassium persulfate (PPS) as an initiator. By changing the molar ratio of CS:NIPAAm from 1:0.25 to 1:10 graft copolymers with a CS backbone and different amounts of PNIPAM side chains were prepared. The chemical structure of the obtained CS-g-PNIPAAm copolymers was confirmed by FTIR and 1H NMR spectroscopy. 1H NMR spectra were also used to calculate the content of attached PNIPAAm side chains. Moreover, the lower critical solution temperature (LCST) behavior of synthesized copolymers was assessed by cloud point, differential scanning calorimetry and particle size measurements. The aqueous solutions of copolymers containing ≥12 molar percent of PNIPAAm side chains demonstrated LCST behavior with the phase separation at around 29.0-32.7 °C. The intensity of thermoresponsiveness depended on the composition of copolymers and increased with increasing content of poly(N-isopropylacrylamide) moieties. The synthesized thermoresponsive chitosan-graft-poly(N-isopropylacrylamide) copolymers could be potentially applied in drug delivery systems or tissue engineering.

Preparation and identification of green polymers towards the production of sustainable latex from β-myrcene and some methacrylate monomers

Sustainable polymers have enough potential to overcome petroleum materials and not completely rely on them for the presence of renewable raw materials, as well as the possibility of developing polymerization methods for renewable raw materials to have these materials recyclability, biodegradability and being a non-toxic material. This has been the focus of recent years. Solvent-free emulsion copolymerization of β-myrcene, a naturally occurring monoterpene monomer, the co-monomers that were used with β-myrcene, tetrahydrofurfuryl methacrylate, iso-bornyl methacrylate, and tert-butyl methacrylate, and each methacrylate monomer was polymerized separately with β-myrcene monomer, β-myrcene –methacrylate monomer (MY/MA) copolymers of different compositions were synthesized under nitrogen atmosphere at 60 ºC, using copolymers composition 50/50 comonomer reactivity ratios, and has been added sodium dodecyl sulfate as emulsifier, and ammonium persulfate as initiator. 1H-NMR, 13CNMR and FTIR spectroscopy were used to confirm the chemical structure and composition. It was found that the copolymerization reaction of each copolymer is influenced with the form of the methacrylate(s) side chain. Furthermore, the thermal properties of copolymers were characterized by DSC and TGA, where the value Tg indicate that random composition copolymers, due to the difference in crystallization of each side chain.

Development and Advantages of Biodegradable PHA Polymers Based on Electrospun PHBV Fibers for Tissue Engineering and Other Biomedical Applications.

Biodegradable polymeric biomaterials offer a significant advantage in disposable or fast-consuming products in medical applications. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is an example of a polyhydroxyalkanoate (PHA), i.e., one group of natural polyesters that are byproducts of reactions taking place in microorganisms in conditions with an excess carbon source. PHA polymers are a promising material for the production of everyday materials and biomedical applications. Due to the high number of monomers in the group, PHAs permit modifications enabling the production of copolymers of different compositions and with different proportions of individual monomers. In order to change and improve the properties of polymer fibers, PHAs are combined with either other natural and synthetic polymers or additives of inorganic phases. Importantly, electrospun PHBV fibers and mats showed an enormous potential in both the medical field (tissue engineering scaffolds, plasters, wound healing, drug delivery systems) and industrial applications (filter systems, food packaging). This Review summarizes the current state of the art in processing PHBV, especially by electrospinning, its degradation processes, and biocompatibility studies, starting from a general introduction to the PHA group of polymers.

Two-step synthesis of polystyrene sulfonate based copolymers bearing pendant primary amines

Polyelectrolytes are macromolecular building blocks which find numerous applications in the design of colloids, interfaces, gels and membranes. Herein, new functional polyelectrolytes copolymers bearing pendant primary amines have been synthesized through the free radical copolymerization of sodium p-styrene sulfonate (SS) and acrylamide (AAm) or chloromethylstyrene (CMS) followed by a post-polymerization modification. The first strategy relies on the use of the Hofmann reaction to convert polystyrene sulfonate-polyacrylamide (P(SS-co-AAm)) copolymers into polystyrene sulfonate-polyvinylamine (P(SS-co-VA)) copolymers. The second route includes the N-alkylation of polystyrene sulfonate-polychloromethylstyrene (P(SS-co-CMS)) copolymers with 1,8-diamino-3,6-dioxaoctane (DADO). It was observed that the chemical modification of P(SS-co-AAm) copolymers of different composition through the Hofmann reaction was effective but lead to some side reactions. In addition, P(SS-co-CMS) copolymers of several composition were prepared in anhydrous DMSO to prevent the early hydrolysis of the CMS units, and were quantitatively post-modified at RT with an excess of DADO. The resulting copolymers were soluble in both water and DMSO, and preliminary experiments on their properties evidenced both the reactivity of their amino group toward reductive amination (either performed with propanal or onto an oxidized nanocellulose), and their polyampholyte behavior at pH below the amine pKa.

Thermal Stability and Kinetics of Thermal Decomposition of Statistical Copolymers of N-Vinylpyrrolidone and Alkyl Methacrylates Synthesized via RAFT Polymerization

The thermal stability and the kinetics of thermal decomposition of statistical copolymers of N-vinylpyrrolidone (NVP) with the alkyl methacrylates, hexyl methacrylate (HMA) and stearyl methacrylate (SMA), were studied by Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG). Statistical copolymers of different compositions were studied, and their thermal decomposition behavior was compared to the corresponding homopolymers. The activation energies of the thermal decomposition were calculated using the Ozawa-Flynn-Wall, the Kissinger, and the Kissinger-Akahira-Sunose methodologies. The effects of the nature of the methacrylate monomer, the copolymer composition, and the rate of heating are discussed.

SYNTHESIS AND INVESTIGATION OF COPOLYMERS OF GLYCIDYLMETHACRYLATE AND COPPER COMPLEX METHYL PHEOPHORBIDE “A” IN SOLUTION

The actual direction in the field of creating new functional materials is a complex study of the influence of tetrapyrrole macroheterocyclic compounds on the processes of radical (co)polymerization with widely used monomers, as well as the development of a general approach to the synthesis and study of the properties of such polymer materials. Promising macroheterocyclic compounds are chlorophyll derivatives of various structures. For this purpose, by the method of solution radical copolymerization in toluene and tetrahydrofuran the copolymers of glycidylmethacrylate and copper complex of methylpheophorbide “a” of various compositions were obtained. Identification of the obtained copolymers and investigation of their structure and properties were performed using data from IR, NMR spectroscopy of compounds, elemental and chemical analysis methods. The synthesized copolymers are characterized by molecular-weight characteristics which were determined by gel-permeation chromatography. It was found that the introduction of a copper complex of methylpheophorbide “a” into the copolymer leads to a decrease in the copolymerization rate, the values of the molecular masses of copolymers and an increase in their polydispersity. The effect of solvents on the time of the copolymerization process and the molecular weight characteristics of copolymers is shown. The composition of the obtained copolymers was determined spectrophotometrically by the optical density of their solutions at the maximum of the first absorption band of the copper complex of methylfeoforbide “a”. Comparison of the intensity of bands in the IR spectra of copolymers of different compositions showed that the content of methylpheophorbid links in the polymer chain increases with the increase in the content of porphyrin in the polymerized mixture. The study of the influence of the nature of the solvent and its structural features on chemical reactions involving porphyrin derivatives allowed us to establish that from a thermodynamic point of view, the best solvent for porphyrinpolymers is toluene.

Batch binding studies with thermo-responsive polymer grafted sepharose 6 fast flow sorbents under different temperature and protein loading conditions

This study has examined the batch binding behaviour of different thermo-responsive co-polymer grafted chromatographic materials under different temperature and protein loading conditions. The effect of molecular composition of poly(N-isopropylacrylamide) (PNIPAAm)-based co-polymers on the phase transition properties has been documented. Sixteen co-polymers of different compositions were synthesized by free radical polymerization methods. Most underwent relatively sharp phase transitions upon application of increasing temperature. However, the value of the lower critical solution temperature (LCST) varied due to differences in co-polymer compositions. In general, it was found that the LCST increased for co-polymers containing more hydrophilic moieties, but decreased for co-polymers with more hydrophobic moieties. Moreover, the LCST increased, together with increased width of the transition temperature, when highly branched monomeric moieties (i.e. N‑tert‑octyl groups) were present. When bulky side chains (octadecyl or triphenylmethyl groups) were located in the polymer structures the LCST transition was absent. Based on these findings, 6 thermo-responsive co-polymers of different compositions were individually immobilised onto cross-linked Sepharose 6 Fast Flow by a “grafting-from” method. Bovine holo-lactoferrin and bovine holo-transferrin at different concentrations in the range 1–100 mg/mL were then employed as target proteins to evaluate the adsorption behaviour under batch binding conditions with these different polymer grafted Sepharose 6 Fast Flow sorbents at two different temperatures. In general, all sorbents exhibited greater affinity and adsorption capacity for bovine holo-lactoferrin at 50 °C compared to 20 °C. In addition, the affinity and adsorption capacity of bovine holo-lactoferrin with positively charged copolymer grafted Sepharose 6 Fast Flow chromatographic sorbents at 20 °C and 50 °C were much lower than that found for negatively charged copolymer grafted Sepharose 6 Fast Flow sorbents, whilst the opposite trend was found with bovine holo-transferrin due to differences in the surface charge properties of these two proteins, indicative of different separation selectivity. Furthermore, the structure of the side chains present in the grafted copolymer structure was found to affect the adsorption performance of both proteins at 20 °C and 50 °C.

Controlling the thermal response of poly(N-isopropylacrylamide)-poly(ethylene glycol)- poly(N-isopropylacrylamide) triblock copolymers in aqueous solution by means of additives

The present work describes how the thermal response of some thermosensitive poly(N-isopropylacrylamide)-poly(ethylene glycol)-poly(N-isopropylacrylamide) (PNIPAM-PEG-PNIPAM) triblock copolymers of different compositions, in aqueous solution, estimated by the cloud point (CP) method, can be controlled by factors like polymer concentration (0.05–5 wt%) and composition (PNIPAM and PEG blocks length, overall polymer hydrophilicity), as well as by the nature and concentration (0.1–0.4 M) of some water-soluble additives. The experiments showed that CP decreased with polymer concentration and molecular weight (MW) of the PNIPAM block and increased with the MW of the PEG block. The influence of inorganic and organic salts through both their anion and cation, and short-alkyl chain organic nonelectrolytes through their alkyl chain architecture (linear or branched) and polarity of the functional group (alcohol, aldehyde, amine, carboxyl) was also investigated. Neither the composition nor the hydrophilicity of our triblock copolymers displayed any appreciable influence upon CP increase/decrease in the presence of additives. It was proved by hysteresis loop area measurements that NaCl addition increased the hysteresis effect of the polymer soluble - insoluble reversible transition.

Preparation and Characterization of Intramuscular PLGA Based Microsphere

The current studies was design and evaluate biodegradable PLGA microspheres for sustained or extended release, with primary goal of avoiding combination of oral therapy for the treatment of schizophrenia. PLGA copolymers 75:25 was used to prepare four microsphere formulations of anti-psychotic drug Olanzapine. The microspheres were characterized by in-vitro dissolution and other physio-chemical methods. A simulation of multiple dosing at weekly or 15-day regimen revealed pulsatile behavior for all formulations with steady state may be achieved by the second dose. Overall, the in-vitro study of Formulations 001, 002, 003, or 004 will eliminate the need for combination oral therapy and reduce time to achieve steady state, with a smaller washout period upon duration of therapy. Results of this study prove the suitability of using PLGA 75:25 copolymers of different composition and molecular weight to produce sustained or extended release formulations that can enhance pharmacological effectiveness for anti-psychotic intra-muscular administration of Olanzapine.
 Keywords: sustained release, PLGA microspheres, Olanzapine

Controlled Spacing between Nanopatterned Regions in Block Copolymer Films Obtained by Utilizing Substrate Topography for Local Film Thickness Differentiation.

Various types of devices require hierarchically nanopatterned substrates, where the spacing between patterned domains is controlled. Ultraconfined films exhibit extreme morphological sensitivity to slight variations in film thickness when the substrate is highly selective toward one of the blocks. Here, it is shown that using the substrate's topography as a thickness differentiating tool enables the creation of domains with different surface patterns in a fully controlled fashion from a single, unblended block copolymer. This approach is applicable to block copolymers of different compositions and to different topographical patterns and thus opens numerous possibilities for the hierarchical construction of multifunctional devices.

Oxidative Copolymerization of <i>o-</i>Hydroxy-<i>m</i>-Phenylenediamine and <i>O</i>- Toluidine - Synthesis, Structure and Properties of Copolymers

Oxidative copolymerization of o-hydroxybenzylidene-m-phenylenediamine and o-toluidine in a solution of sulfuric acid synthesized new copolymers of different composition. Structures of the copolymers obtained were confirmed by IR spectroscopy. It is shown that the copolymers obtained are not fusible materials and acid-soluble materials. The synthesized copolymers have been found to possess sufficient thermostability. The process of decomposition of the copolymers occurs in several stages, the temperature ranges depending on their composition.

Towards the higher solubility and thermal stability of poly(aniline-co-m-bromoaniline)

In the current study, we have described the synthesis and the physical properties of poly(aniline-co-m-bromoaniline) conducting copolymers. The copolymers of different composition are essentially obtained by varying the molar feed ratio of the two monomers. The higher solubility of the copolymers could be procured as compared to polyaniline (PA) in different solvents. The electrical conductivity has been studied by two-probe method; at room temperature, the conductivity of the copolymer decreases upon increasing the molar ratio of m-bromoaniline monomer. The introduction of bromine (–Br) group reduces the degree of conjugation in the polymer chain. Thus, conduction of electrons is prohibited along the conjugated system. In the thermogravimetric analysis (TGA), a three-stage decomposition of the copolymer has been observed. The copolymers of poly(aniline-co-m-bromoaniline) are thermally stable at high temperature. The composition of the copolymer has been confirmed from the binding energies of C–C, C–N, and C–Br in the XPS study.

НОВЫЕ ТЕРМОСТОЙКИЕ ФУНКЦИОНАЛЬНЫЕ СОПОЛИМЕРЫ

The interaction of vinyl acetate with 1-vinyl-1,2,4-triazole under conditions of free radical initiation of functional copolymers, containing hydrophilic triazole and hydrophobic acetate fragments in their structure, are synthesised. In order to obtain copolymers of different composition that are well-soluble in water and organic solvents, the ratio of monomers in the initial reaction mixture was varied. By evaluating the reactivity of monomers, it was established that 1-vinyl-1,2,4-triazole exhibits greater reactivity compared to vinyl acetate. Copolymers exhibiting the properties of high-resistance organic semiconductors, characterised by a specific electrical conductivity of the order 10 -14 -10 -15 S/cm, have high resistance to thermal-oxidative degradation: the beginning of thermal decomposition occurs at temperatures of 300-330 °C. The structure, composition and physicochemical properties of the copolymers were characterised by elemental analysis methods, IR and NMR 1 H spectroscopy, turbidimetric titration, as well as thermogravimetric analysis.

Functional copolymers with triazole and acetate fragments

New functional copolymers of different composition with triazole and acetate fragments in the macromolecules were synthesized by free radical copolymerization of 1-vinyl-1,2,4-triazole with vinyl acetate. The reactivity of the comonomers was studied and the monomer copolymerization constants were calculated. The structure and composition of the copolymers were determined by elemental analysis, IR and 1H NMR spectroscopy.

2-Hydroxyethylcellulose and Amphiphilic Block Polymer Conjugates Form Mechanically Tunable and Nonswellable Hydrogels

Herein, we report a family of mechanically tunable, nonswellable hydrogels that are based on a 2-hydroxyethylcellulose (HEC) scaffold grafted with amphiphilic diblock copolymers. Poly[(oligo(ethylene glycol)methyl ether methacrylate]-b-poly(methyl methacrylate) (POEGMA-b-PMMA) diblock copolymers of different compositions were created via RAFT polymerization using an alkyne terminated macro chain transfer agent (CTA). 2-Hydroxyethylcellulose (HEC) was modified with azide groups and the diblock copolymers were attached to the backbone via the copper-catalyzed click reaction to yield HEC-g-(POEGMA-b-PMMA) graft terpolymers. The resulting conjugates were soluble in DMF and able to form hydrogels upon simple solvent exchange in water. By increasing the concentration of the conjugates in DMF, the storage moduli of the hydrogels increased and the pore size in the gel decreased. After hydrogel formation, the structures were also found to be nonswellable (no macroscopic volume change upon incubation in water), which is an important feature for retaining size and mechanical integrity of the gels over time. Moreover, these materials were able to be electrospun into fibers that, upon hydration, formed fibrous hydrogel structures. The nonswellable and tunable mechanical properties of these materials imply great potential for a variety of applications such as personal care, active delivery, and tissue engineering.

Tuning the spectral, thermal and fluorescent properties of conjugated polymers via random copolymerization of hole transporting monomers

Effect of copolymerization on the fluorescent properties of polycarbazole and poly(o-phenylenediamine).

Thin films from hydrophilic poly(N,N-dimethyl acrylamide) copolymers as optical indicators for humidity

In the present paper we study thin films from poly(N,N-dimethyl acrylamide)-poly(ethylene oxide) (PDMAA/PEO) copolymers of different composition and structure in order to implement them as sensitive media for optical indicators for humidity. PDMAA/PEO di- and triblock copolymers were synthesized via redox polymerization in aqueous media. Thin films were deposited on silicon substrates by spin coating method using polymers solutions with appropriate concentrations. Refractive index, extinction coefficient and thickness of the films are calculated from reflectance spectra of the films deposited on silicon substrates using non-linear curve fitting method. Sensing properties of the films were tested by films exposure to different humidity levels followed by in-situ monitoring of the changes in the optical properties. The influence of the polymer structure and postdeposition annealing on the optical and sensing properties of the films was investigated. The potential application of selected polymers for optical sensing of humidity were demonstrated and discussed.

Amphiphilic Block Copolymers as Stabilizers in Emulsion Polymerization: Effects of the Anchoring Block Molecular Weight Dispersity on Stabilization Performance

Poly(sodium acrylate)-b-polystyrene block copolymers were employed as stabilizers in the emulsion polymerization of styrene. Previous work by our group has shown that the molecular weight dispersity of the stabilizing block is an important design parameter of block copolymer stabilizers; herein, the molecular weight dispersity of the anchoring polystyrene block, ĐPS, was investigated. Stabilization performance was evaluated by the critical aggregation concentration, aggregation number, and surface activity of the block copolymers and the size, distribution, and zeta potential of the polystyrene latex particles. It was observed that ĐPS had a strong effect on aggregation number, which led to a change in the number of latex particles in the seeded emulsion polymerization of styrene. Surface activity decreased with increasing ĐPS due to a greater diversity of copolymer compositions, supporting the idea that copolymers of different composition play different roles in the stabilization of an emulsion. The perf...

Anticorrosion activity of aniline–aniline-2-sulfonic acid copolymers on the steel surface

The structure and barrier properties of layers formed on the interface of steel with aniline–orthanilic acid copolymers of different compositions were determined. The structure of the protective system ensuring the best anticorrosion properties was found.

1-Vinyl-1,2,4-triazole in copolymerization reaction with 1-vinyl-4,5,6,7-tetrahydroindole: synthesis and properties of copolymers

A radical copolymerization of 1-vinyl-1,2,4-triazole (VTA) with 1-vinyl-4,5,6,7-tetrahy-droindole (VTHI) was studied. New thermally stable functional copolymers of different composition, well soluble in organic solvents were synthesized. It was found that VTA has higher reactivity as compared to VTHI. A new soluble polymeric nanocomposite with metallic silver nanoparticles encapsulated into the matrix of synthesized copolymer was obtained.