Study of LCST of thermo-sensitive polymers in mixed system

Poly(N-isopropylacrylamide)(PNIPAm) and P(NIPAm-co-KYD) copolymer exit a lower critical solution temperature(LCST) in aqueous solution which is about 33℃,14℃ and 4℃,respectively.The effect of one or multi-factor(additions) on LCST of PNIPAm or P(NIPAm-co-KYD) aqueous solution,such as cationic surfactant(CTAC),EDTA,salt or ionic/nonionic polymer were studied in this paper.It was found that the LCST decreased to 25℃ abruptly when the concentration of EDTA was 0.1% in the system in the absence of CTAC.With further increase in concentration of EDTA,the LCST changed more slowly 2℃ than before.However,the effect of CTAC differed greatly from EDTA.The phenomenon of polymers coil-to-globe transition was no longer clear in the system containing 0.5-1.0% CTAC and there was a little decrease in LCST when higher than 1.5%,accompanying the clear phase transition again.Salt could make the LCST of the system drop in line,which was meaningful as guidance in theory.It was found that changes of LCST were mild as we studied the effect of multi-factor on LCST.