Polymer Science, Series A

Sodium salt of styrene/methacrylic acid copolymer was synthesized via radical polymerization, and its absolute molecular mass and polydispersity index were measured by aqueous-based GPC coupled with MALLS in a mixed solvent containing 75/25, v/v%, methanol/water, 38.6 mM NaCl and 10.0 mM NaH2PO4 buffer, pH 6.0. Dynamic light scattering verified the absence of aggregation of copolymer in preferred mobile phase compositions.

Poly(vinyltrimethylsilane) and poly(1-trimethylsilyl-1-propyne) are metallated using normal and secondary butyllithium chelate complexes with tetramethylethylenediamine and superbases based on complexes of normal and secondary butyllithium with potassium tert-pentoxide as metallating agents. Optimal conditions ensuring metallation of poly(vinyltrimethylsilane) and poly(1-trimethylsilyl-1-propyne) with a high yield without degradation of macrochains are determined. Poly(vinyltrimethylsilane) and poly(1-trimethylsilyl-1-propyne) are functionalized via reactions of metallated polymers with CO2, trimethylsilyl chlorosulfone, diethyl disulfide, and ethylene oxide. COOH, SO3H, OH, and thioester groups are introduced into poly(vinyltrimethylsilane), and SO3H and COOH groups are incorporated into poly(1-trimethylsilyl-1-propyne). Upon introduction of carboxyl groups into poly(vinyltrimethylsilane), its hydrophilicity and permselectivity with respect to H2O/N2, H2O/H2, and H2O/CH4 pairs increase. The introduction of SO3H groups into poly(1-trimethylsilyl-1-propyne) and poly(vinyltrimethylsilane) leads to the appearance of proton conductivity of these polymers.

Chitosan is a chitin-derived biopolymer characterized by excellent bioactive properties, such as biodegradability and biocompatibility. In addition, due to its high film forming capability, chitosan is emerged as a promising natural polymer for tissue engineering. However, its application areas can be further extended by the improvement of its poor mechanical properties. In this context, the current work aimed to characterize the mechanical and physicochemical properties of α‑chitin whiskers-reinforced chitosan nanocomposite films (WRC-films). For this purpose, WRC-films were developed through the incorporation of an α-chitin obtained from Parapenaeus longirostris shrimp shells. Then, their physico‑mechanical properties, mainly the tensile strength and percentage of elongation at break, were compared with pure chitosan films (PC-films). The WRC-films showed an increased tensile strength, and a decreased percentage of elongation at break, compared to pure chitosan films. Altogether, these results plead in favor of the use of chitin whiskers as an additive in chitosan film matrix. In addition, to our knowledge this is the first report on the chitosan film reinforcement through the incorporation of the α-chitin extracted from the exoskeleton of Parapenaeus longirostris.

The behavior of two charged polymer networks in a solution of an oppositely charged surfactant was studied. It was shown that such a system (depending on preset parameters) can exist in different modes: without micelles in both networks, with micelles in one of the network, and with micelles in both networks. The dependences of network dimensions and ion concentrations inside the networks on the surfactant concentration in the solution, the fraction of charged units in one of the networks, and the relative size of the system were obtained. It is possible to affect the state of one network by varying the parameters (e.g., the proportion of charged units) of the other network. Different network swelling scenarios depending on the relative size of the system and the fraction of charged network units were revealed.

Dielectric polarization of solutions of un-ionized linear poly(methacrylic acid) in polar associated liquids is studied in the temperature range 20–50°C. The solutions are in methanol, with the molar fraction of polymer units x 2 = (3 × 10−3)−(1.5 × 10−2), and in water, with x 2 = (4 × 10−5)−(4 × 10−3). The permittivity ε12 of the polyacid solutions in methanol is shown to be lower than the permittivity of the pure solvent ε1; the permittivity of the polyacid solutions in water exceeds ε1 of water in the concentration range x 2 = (4 × 10−5)−(2.13 × 10−4) and becomes lower than ε1 as the polymer concentration in the solution increases further. A procedure for estimating the dipole moment μ2 per monomer unit of the polymer macromolecule in solution is proposed. The estimation is based on Buckingham’s statistical polarization theory for a two-component mixture of polar molecules under the conditions of infinite dilution. The μ2 values amount to 2.76–2.14 D (x 2 < 1.5 × 10−2) in methanol at 20–50°C and to 11.4−3.8 D (x 2 < 2.13 × 10−4) in water at 20–40°C. The difference in the dipole moments of the polyacid and in the patterns of their temperature dependences in methanol and in water is due to the effects of the polyacid-solvent hydrogen bonding, to intramacromolecular hydrogen bonds, and to specificity of the local structure of the solvent. It is shown that the μ2 value corresponds to the dipole moment of the solvates and decreases with temperature owing to changes in the stoichiometry of the solvates, to the formation of cyclic associates in the macromolecule, and to conformational changes in the chain.

The specific features of the stress-induced shape memory effect are studied for composites based on various polymers and fillers, which can form aggregates and are capable of marked compaction. The appropriate deformation schemes make it possible to prepare composites with different structural states, which give various signs and ratios between longitudinal and transversal strains upon shape recovery. The criterion is proposed for estimating the ability of the composite for shape recovery with marked volume changes: the relative density of the filler defined as the ratio of powder density and compacted powder density.

New polyamic acids with biquinoline units in the backbone, which are prepolymers of polybenzoxazinones, as well as their metal-polymer complexes containing [Ru(bpy)2]2+, were prepared. The electronic structure of these polymers was studied with the use of cyclic voltammetry, electronic absorption spectroscopy, and quantum-chemical calculations, and the location sites of electronic changes upon electrochemical reduction and oxidation were determined.

The local mobility and organization of micelles formed by the cationic diblock copolymer PS-poly(N-ethyl-4-vinylpyridinium bromide) in dilute aqueous solutions is studied by spin-probe ESR spectroscopy. Micelles composed of a hydrophobic PS core and a lyophilizing polyelectrolyte corona are prepared by two methods: dialysis from a nonselective solvent and direct dispersion of the diblock copolymer in water under long-term heating. Velocity-sedimentation studies and static and dynamic light-scattering measurements show that the micelles obtained by dialysis have smaller mean hydrodynamic sizes and weight-average molecular masses and are less polydisperse than micelles prepared by direct dispersion. The ESR spectra of spin probes localized in micelles of both types are found to be identical. This finding suggests that their local structure is independent of the dispersion procedure and molecular-mass characteristics. Probes are localized in the outer layer of the PS core near the core/shell boundary, and their local mobility is a factor of ∼2 higher than the local mobility of probes in the phase of the solid PS. It is inferred that the structure of the outer layer of the PS core in micelles is looser than the structure of PS in the solid phase. The localization sites of spin probes are partially penetrated by water.

A thorough understanding of pesticide fate in soil and replacement of traditional pesticide formulations with polymeric controlled release pesticide formulations may provide a preventive approach for safer and more effective application of pesticides in the field. In this direction, the present study discusses the soil adsorption study of atrazine herbicide on Indian soil and synthesis of polymeric controlled release formulation based on Azadirachta indica (Neem) (AI) leaf powder and sodium alginate. The value of Ground Ubiquity Score (GUS) for atrazine herbicide has been observed 2.58 which classifies it as a transition pesticide in terms of ground water contamination with higher Environment Exposure Potential (EEP) in Indian soil. Polymeric controlled release pesticide formulations (CRPFs) were synthesized by ionotropic gelation method with three different crosslinking ions i.e. Ca2+, Ba2+, and Al3+. These CRPFs have been characterized by FTIR, SEM-EDAX and TGA. Polymeric CRPFs released the herbicide in controlled manner for a period of 300 h and followed non-Fickian diffusion mechanism. AI-Alginate-Ca beads showed maximum cumulative release 14.99 mg/g in 300 h, followed by BaCl2 and AlCl3 crosslinked beads. The release study showed that the Polymeric CRPFs can be effective in controlling the release and adverse effects of atrazine in the environment.