Poly(NIPAM) microgel particle de-swelling: a light scattering and small-angle neutron scattering study

详细信息    查看全文

• 作者：Crowther ; Helen M. ; Saunders ; Brian R. ; Mears ; Sarah J. ; Cosgrove ; Terence ; Vincent ; Brian ; et. al.
• 关键词：SANS ; Poly(NIPAM) ; Swelling ; Microgel ; Thermosensitive
• 刊名：Colloids and Surfaces A: Physicochemical and Engineering Aspects
• 出版年：1999
• 出版时间：July 31, 1999
• 年：1999
• 卷：152
• 期：3
• 页码：327-333
• 全文大小：134 K

文摘

Small-angle neutron scattering (SANS) has been used to investigate structural changes during the de-swelling of poly(N-isopropylacrylamide) [poly(NIPAM)] microgel particles induced by temperature variation and the addition of free polymer [poly(ethylene oxide)]. The extent of particle de-swelling was characterized by photon correlation spectroscopy (PCS). Thermally-induced de-swelling of poly(NIPAM)/deuterated water dispersions occurred on increasing the temperature in the region of the lower critical solution temperature (LCST). The latter was found to be 34°C, which is 2°C higher than the value reported for poly(NIPAM) particles dispersed in water. The SANS data exhibit a Porod form (Q⁻⁴) of scattering in regard to the size of the colloidal particles. However, in the swollen state, the scattering measured at temperatures less than the LCST, also has a contribution from poly(NIPAM) chains in a solution-like environment (Ornstein–Zernike scattering). The trends observed in the SANS data as a function of temperature were simulated using a model comprised of Porod and Ornstein–Zernike scattering terms. The SANS data confirm earlier PCS measurements showing that addition of free polymer induces particle de-swelling. The SANS data obtained using added free polymer are the first examples of their type to be reported.