Influence of a Crown Ether Comonomer on the Temperature-Induced Phase Transition of Poly(N-isopropylacrylamide) Hydrogels

详细信息    查看全文

• 作者：Katalin Kosik ; Erzsé ; bet Wilk ; Erik Geissler ; Krisztina Lá ; szló
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：January 31, 2008
• 年：2008
• 卷：112
• 期：4
• 页码：1065 - 1070
• 全文大小：150K
• 年卷期：v.112,no.4(January 31, 2008)
• ISSN：1520-5207

文摘

Copolymerization of thermosensitive hydrogels based on poly(N-isopropylacrylamide) (PNIPA) is a possibleroute to enhanced storage capacity of guest molecules. This article describes the synthesis of the amphiphiliccrown ether N⁹-propenoyl-3,6,12,15-tetraoxa-9,21-diazabicyclo[15.3.1]heneicosa-1(21),17,19-triene (CE) andits incorporation into a PNIPA hydrogel (PNIPA/CE). Mechanical measurements on the gel show that theCE units contribute to the elasticity of the network, but the swelling ratio in water is reduced compared to theunmodified system. The comonomer reduces the temperature of the volume phase transition (VPT), T_VPT,and broadens the transition. Both the enthalpy and the entropy associated with the VPT decrease. Scatteringmeasurements indicate that the local structural features on the scale of 10 Å are unchanged, but the CE unitsform large clusters, the size of which increases with rising temperature. In the phase-separated state aboveT_VPT these clusters are distributed on the polymer-water interface.