Weng Yiming, Ding Yanwei, Zhang Guangzhao
Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui, China.
J Phys Chem B. 2006 Jun 22;110(24):11813-7. doi: 10.1021/jp0616922.
The lower critical solution temperature (LCST) behaviors of random and segmented copolymers of N-isopropylacrylamide (NIPAM) and acrylic acid (AA) prepared in dioxane and water have been investigated by using ultrasensitive microcalorimetry (US-DSC). The introduction of AA increases the LCST of the former but slightly affects that of the latter. When the molar fraction of AA is low (approximately 2 mol %), the LCST of the segmented copolymer shifts to a higher temperature with increasing pH, while the LCST of the corresponding random copolymer slightly changes. Below the boiling point of water, the random copolymer and segmented copolymer with the molar fraction of AA about 15 mol % no longer exhibit an LCST at pH > 5. The addition of calcium ions leads the LCST of both the segmented copolymer and random copolymer to decrease. Our results suggest that the LCST behavior of the copolymers is determined by the clustering of poly(N-isopropylacrylamide) segments.
通过超灵敏微量量热法（US-DSC）研究了在二氧六环和水中制备的N-异丙基丙烯酰胺（NIPAM）与丙烯酸（AA）的无规共聚物和嵌段共聚物的低临界溶液温度（LCST）行为。AA的引入提高了前者的LCST，但对后者的影响较小。当AA的摩尔分数较低（约2 mol%）时，嵌段共聚物的LCST随pH值升高而向更高温度移动，而相应无规共聚物的LCST变化不大。在水的沸点以下，AA摩尔分数约为15 mol%的无规共聚物和嵌段共聚物在pH > 5时不再表现出LCST。钙离子的加入导致嵌段共聚物和无规共聚物的LCST均降低。我们的结果表明，共聚物的LCST行为由聚（N-异丙基丙烯酰胺）链段的聚集决定。
