Stimuli responsive block Copolymers synthesis strategies functionalization And selective applications

Abstract

Gels are an important class of soft materials with numerous newlineapplication potential, such as sensing, drug delivery, etc. A gel is a newlinethree-dimensional crosslinked polymeric network that is swollen in a newlinesolvent (dispersing medium). Gels exhibit densities similar to liquids newlineand have the structural coherence of a solid. A hydrogel is one in newlinewhich the gel network is dispersed in water. In an organogel, an newlineorganic solvent serves as the dispersing medium. In this research newlinework, three different diblock copolymers (BCPs), viz., poly(Nisopropylacrylamide- newlineblock-styrene), PNIPAM-b-PS, poly(styreneblock- newline4-vinylpyridine), PS-b-P4VP, and poly(N-isopropylacrylamideblock- newline4-vinylpyridine), PNIPAM-b-P4VP, were synthesized using newlineRAFT polymerization. Structural elucidation of these BCPs was newlineperformed using 1H NMR and FTIR spectroscopy. Among these newlinethree BCPs, the ones having P4VP were chemically crosslinked to newlineform an organogel, and the dispersing medium was newlinedimethylformamide (DMF). newlineThe PNIPAM-b-PS showed a unique temperaturedependent newlinemicelle formation at 34 °C. Though this polymer flowed at newlinea very high concentration, rheological studies showed that the sample newlinemanifested solid-like behaviour with Gand#8242; gt Gand#8243;. The modulus showed newlinefrequency-dependence, and the magnitude of Gand#8242; was two-fold higher newlinethan Gand#8243;, implying a weak gel state. Weak gel states are generally newlinenoted at high temperatures in most of the polymer systems; contrary newlineto this, the PNIPAM-b-PS showed weak gel states at a lower newlinetemperature.