SYNTHESIS AND CHARACTERIZATION OF A THERMAL SENSITIVE POLYELECTROLYTE BASED ON POLY(VINYL ALCOHOL) AND ITS THERMAL SENSITIVE PROPERTIES

Abstract

Thermo-sensitive polymers have gained great interest in recent years due to the unique features facilitating their applications in a variety of areas,such as controlled drug release,biotechnology,separation,etc.They exhibit fast,reversible volume changes around their lower critical solution temperature (LCST).More recently,much attention has been paid to the preparation of ionic thermo-sensitive polymers because polyions are readily adsorbed on the surfaces with opposite charges and polycations have been proposed as novel non-viral vectors for gene delivery.It is well known that PVA is a cost-effective,low toxic and biocompatible polymer.Not only applied to industrial products such as fibers,coatings and films,PVA has also been utilized in biomedical applications,such as artificial kidney,pancreas,etc.In this paper,glycidyltrimethylammonium chloride(GTMAC) and acetaldehyde were selected to modify(poly(vinyl) alcohol)(PVA) in an attempt to render PVA thermo-sensitive and cationic characters,where the GTMAC introduces cationic groups whereas acetaldehyde provides hydrophobic ethyl groups.The structure of modified PVA(CAPVA) was characterized by elemental analysis,surface charge density and NMR.And the thermo-sensitivity or LCST was revealed by using a turbidimeter.It is found that CAPVA is water-soluble and generates clear aqueous solution below LCST.As the temperature rises above LCST,the chains are hydrophobically associated or aggregated,leading to phase separation of the formation of CAPVA agglomerates.The LCST of CAPVA was influenced by the amount of cationic groups,the degree of acetalysis and the concentration of NaCl in solution.The LCST of CAPVA containing more cationic groups and less acetal rings was relatively high(up to 75℃),which was lowered gradually with the increase of NaCl concenrtration.The LCST of CAPVA can be tailored or adjusted via controlling the densities of cationic groups and acetal rings as well as the electrolyte concentration.