Effect of LCST on the swelling of PAAm-NIPA copolymers: a fluorescence study


Evingur G. A. , Pekcan O.

POLYMER BULLETIN, cilt.68, ss.223-238, 2012 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 68 Konu: 1
  • Basım Tarihi: 2012
  • Doi Numarası: 10.1007/s00289-011-0625-6
  • Dergi Adı: POLYMER BULLETIN
  • Sayfa Sayıları: ss.223-238

Özet

Temperature sensitive copolymers were prepared by free radical crosslinking copolymerization in aqueous solution with different molar percentage of N-isopropylacrylamide (NIPA) and acrylamide (AAm) monomers. N,N'-methylenebis (acrylamide) (BIS) and ammonium persulfate (APS) were used as a crosslinker and an initiator, respectively. The steady-state fluorescence (SSF) technique was used to determine the low critical phase transition temperature (LCST) for PAAm-NIPA copolymers. Swelling experiments were performed in water at various temperatures by real time monitoring of pyranine (Py) fluorescence intensity, I which decreased as swelling proceeded. The Stern-Volmer equation is modified for low quenching efficiencies to interpret the behavior of pyranine intensity during the swelling of PAAm-NIPA copolymers. The Li-Tanaka equation was used to determine the swelling time constants, tau (1) and the cooperative diffusion coefficients, D (0) from fluorescence intensity, weight and volume variations of the copolymers at various temperatures. It was observed that tau (1) first increased up to LCST, and then decreased; naturally D (0) decreased up to LCST and then increased upon increasing temperature. It was understood that (LCST) increases as PAAm contents increase in the PAAm-NIPA copolymers.