Departamento de Química Física, Facultad de Química, University of Murcia, Murcia, Spain.
J Phys Chem B. 2010 Jul 15;114(27):8887-93. doi: 10.1021/jp102442q.
A bead-and-spring model has been used to simulate the behavior of thermoresponsive asymmetric diblock amphiphilic copolymers with aid of Monte Carlo simulations. The alteration of the thermodynamic conditions was mimicked by using a Lennard-Jones potential, which was related to the measured temperatures by comparison with experimental data for aqueous solutions of two sets of diblock copolymers, namely methoxypoly(ethylene glycol)-block-poly(N-isopropylacrylamide), one with different lengths of the hydrophilic block (MPEG(n)-b-PNIPAAM(71)) and one with varying lengths of the hydrophobic block (MPEG(57)-b-PNIPAAM(m)). The influence of the length of both the thermoresponsive and the hydrophilic block on the size and conformation of single molecules at various temperatures was studied by means of simulations. The temperature-induced contraction of the copolymer (MPEG(n)-b-PNIPAAM(71)) entities is only modestly affected by changing the length of the hydrophilic block, whereas for the MPEG(57)-b-PNIPAAM(m) copolymer both the transition temperature and the magnitude of the compression of the molecules are strongly influenced by the length of the thermosensitive block. When the MPEG chain fully covers the hydrophobic core, the copolymer moieties are stabilized, whereas poorly covered cores can promote interchain aggregation at elevated temperatures.
采用珠-簧模型，借助蒙特卡罗模拟对具有热响应性的不对称两亲性嵌段共聚物的行为进行了模拟。通过使用 Lennard-Jones 势能来模拟热力学条件的变化，该势能通过与两组嵌段共聚物（即甲氧基聚（乙二醇）-嵌段-聚（N-异丙基丙烯酰胺））的水溶液的实验数据进行比较，与测量温度相关联，这两组嵌段共聚物的亲水链段长度不同（MPEG(n)-b-PNIPAAM(71))和一个疏水链段长度不同（MPEG(57)-b-PNIPAAM(m)）。通过模拟研究了在不同温度下，亲水性和热响应性链段的长度对单分子尺寸和构象的影响。共聚物（MPEG(n)-b-PNIPAAM(71))实体的温度诱导收缩受改变亲水链段长度的影响不大，而对于 MPEG(57)-b-PNIPAAM(m)共聚物，分子的转变温度和压缩幅度都受热敏链段长度的强烈影响。当 MPEG 链完全覆盖疏水核时，共聚物链段得到稳定，而未充分覆盖的核在高温下可以促进链间聚集。
