雙親性高分子自組裝結構之研究

Abstract

本文研究範圍主要分為三部份，第一部份是模擬組成固定為 的高分子，在不同結構的型態變化。這部份又可分成親溶劑段的影響和疏溶劑段的影響兩方面討論。要達成最好的保護效果，親溶劑段的長度不宜過長，但也不可太短，利用長度的限制包覆核是最佳選擇；若能將疏溶劑段以親溶劑段區分成許多小單位，也可使保護力增加，甚至會出現單一高分子微胞的穩定型態。 第二部份討論的是疏溶劑性粒子和溶劑間的作用力參數，當分子量較小時，微胞受作用力參數影響較明顯，作用力參數大時，會幾乎糾結成一巨大微胞，且形狀成不規則狀；當作用力參數較小時，會呈鬆散排列，甚至不會發生聚集的現象。當分子量較大時，作用力參數幾不會對型態產生影響，聚集數都維持在一定值。 第三部份討論的是組成比例造成的影響。小形梳狀高分子和較大的梳狀高分子，會有不同的型態，前者皆為球型，後者可能變成不規則型狀。由於梳狀共聚物變因太過複雜，故本文僅對線性共聚物加以討論。疏溶劑性分子較多的情況，聚集數會隨分子量上升而快速下降，然後再緩慢上升。其原因為殼層厚度太薄，無法保護核的部份，因此才需和其他高分子聚集，分子量較大時，核的表面積增加幅度緩慢，所以聚集數的上升趨勢較緩。當親溶劑性分子較多時，分子量小時聚集數會上升，之後會維持水平，原因為過長的親溶劑段保護效率不好，因此造成此結果。

Block copolymers have attracted significant scientific and economic interest over the past few decades due to their ability to self-assemble into ordered structures. In a selective solvent, i.e. a thermodynamic good solvent for the one block and precipitant for the other, block copolymers associate and form micellar aggregates, which resemble the micelles obtained from the low molecular weight surfactants. Block copolymer micelles consist of a more or less swollen core of the insoluble blocks surrounded by a corona formed by the soluble blocks. Because of their stability, variety of sizes, micelles can be used in a diverse field of practical applications, such as controlled drug delivery and surface modification. In this work, Dissipative Particle Dynamics was used to study the aggregative behavior of block copolymers with different complex structures in selective solvents. It was found that with proper arrangements of the solvophilic blocks, micelles with various sizes and shapes would form. For example, for AxB24Ay triblock linear copolymers (where x+y=24) in a selective solvent for A blocks, the aggregation number reaches a minimum value when x = y and gradually increases as x/y deviates from 1. For a brush copolymers, the aggregation number decreases as the solvophilic side chains becomes more and more homogeneously dispersed along the solvophobic main chains. These results indicate that the macromolecular architecture is a very important factor for the manipulation of the micellar properties. The aggregation number and the overall micellar size can be adjusted through changing the structures of the blocks.