Centro de Quimica Estrutural, Instituto Superior Técnico, Universidade Técnica de Lisboa, 1049-001 Lisboa, Portugal.
Langmuir. 2010 Feb 2;26(3):1807-15. doi: 10.1021/la902510q.
The thermoresponsive behavior of the rhodamine B end-labeled double hydrophilic block copolymer (DHBC) poly(N,N-dimethylacrylamide)-b-poly(N,N-diethylacrylamide) (RhB-PDMA(207)-b-PDEA(177)) and the 1:1 segmental mixture of PDEA and rhodamine B end-labeled PDMA homopolymers was studied over the range of 10-40 degrees C at the air-water interface. The increase in collapse surface pressure (second plateau regime) of the DHBC with temperature confirms the thermoresponsiveness of PDEA at the interface. The sum of the pi-A isotherms of the two single homopolymers weighted by composition closely follows the pi-A isotherm of the DHBC, suggesting that the behavior of each block of the DHBC is not influenced by the presence of the other block. Langmuir-Blodgett monolayers of DHBC deposited on glass substrates were analyzed by laser scanning confocal fluorescence microscopy (LSCFM), showing schizophrenic behavior: at low temperature, the RhB-PDMA block dominates the inside of bright (core) microdomains, switching to the outside (shell) at temperatures above the lower critical solution temperature (LCST) of PDEA. This core-shell inversion triggered by the temperature increase was not detected in the homopolymer mixture. The present results suggest that both the covalent bond between the two blocks of the DHBC and the tendency of rhodamine B to aggregate play a role in the formation of the bright cores at low temperature whereas PDEA thermoaggregation is responsible for the formation of the dark cores above the LCST of PDEA.
在 10-40°C 的温度范围内，在气-水界面研究了罗丹明 B 末端标记的双亲水性嵌段共聚物 (DHBC) 聚 (N,N-二甲基丙烯酰胺)-b-聚 (N,N-二乙基丙烯酰胺) (RhB-PDMA(207)-b-PDEA(177)) 和 PDEA 与罗丹明 B 末端标记 PDMA 均聚物的 1:1 段混合物的温度响应行为。DHBC 的坍塌表面压（第二平台区）随温度升高而增加，证实了 PDEA 在界面上的温度响应性。由组成加权的两种单均聚物的 pi-A 等温线之和非常接近 DHBC 的 pi-A 等温线，这表明 DHBC 的每个嵌段的行为不受另一个嵌段的存在的影响。在玻璃基板上沉积的 DHBC 的 Langmuir-Blodgett 单层通过激光扫描共聚焦荧光显微镜 (LSCFM) 进行了分析，显示出分裂行为：在低温下，RhB-PDMA 嵌段主导明亮（核）微区的内部，在 PDEA 的下临界溶液温度 (LCST) 以上的温度切换到外部（壳）。在均聚物混合物中未检测到这种由温度升高引发的核-壳反转。目前的结果表明，DHBC 两个嵌段之间的共价键以及罗丹明 B 聚集的趋势都在低温下形成明亮核中起作用，而 PDEA 热聚集是在 PDEA 的 LCST 以上形成暗核的原因。
