SILICON-CONTAINING OLIGOMERIC AZOINITIATORS IN THE SYNTHESIS OF BLOCK COPOLYMERS

Abstract

A solvothermal synthetic pathway and functional polymer styabilizers was used for synthesis of fine silver structures of different architecture. Using polyvinylpyrrolidone as a stabilizer silver micronized wires with a diameter of 3,8–4,2 μm and aspect ratio of up to 30 were prepared. XRD technique was applied for qualitative determination of silver metal structures. New thermoresponse composite hydrogels with a structure of semi-IPNs were prepared from cross-linked polyvinyl alcohol, linear highly hydrophilic poly(2-ethyl-2-oxazoline) (PEtOx) and as-synthesized silver micro-sized wires. Effect of a structure and a composition of the polymer matrix, and inorganic anisotropic filler on structure arrangement of composite hydrogels were evaluated by DMA studies. A presence of linear hydrophilic PEtOx and anisotropic metal filler in PVA matrix reduces storage modulus Е’ from 275 to 222–230 MPa and increases loss modulus Е” up to 45,5 MPa at room temperature measurements that partially initiated by poor structuration ability of the composites under high solvation level of polymer matrices. Increasing temperature leads to redistribution of hydrogen bonds network and hybridization of PVA nad PEtOx macrochains and enhances energy dissipation ability of unfilled hydrogel. A filler due to conjugation with amine-functionalized PEtOx chains and its localization closed to a surface of metal supresses polymer-polymer interactions and elasticity parameters of composite matrix drops down. As a result, diffusion and permeability coefficients of composite hydrogels reaches 1,06–1,52·10–9 cm2/s and 0,83–1,09·10-9 g/(cm·s), respectively, that higher in comparison with cross-linked PVA matrices. A presence of hydrogen bonds of different energy in hydrogels provides an appearance of multiple relaxation transitions due to different macrochain mobility in a bulk of polymer matrix. Differences of temperature interval of LCTS for hydrogels were found from analysis Е”(T)/dT (62–70 °С) and Δχ(T)/dT (67–70 °С) dependencies are interrelated with kinetic pecularities of diffusion processes that are able to suppress a phase separation at the temperatures closed to LCTS. Phase inversion processes for hydrogel containing 5 % of PEtOx at LCTS are accompanied by desorption of 32–73 % of sorbate. Moreover, thermoresponsive properties of the hydrogels filled with metallic silver wires are higher than that of the unfilled semi-IPNs.