Precise and Controllable Assembly of Block Copolymers

With the development of nanotechnology,the precise synthesis of nanoparticles with nicely-defined dimensions and structures has been well-developed,and the functionalization and subsequent applications of the resultant nanostructures are becoming increas-ingly important.Comparing to inorganic nanoparticles,the nanostructures based on soft matters,especially block copolymer as-semblies,are much lower in cost,easier to fabricate and richer in morphology.However,the dimensional control over the block co-polymer assemblies is not as easy.Only in recent decade,with the discovery of living Crystallization-Driven Self-Assembly(CDSA)by Manners and Winnik,researchers become able to precisely tune the sizes of block copolymer assemblies in a relatively wide range.This discovery has inspired tremendous research effort in the self-assembly field,and considerable progress has been made recently.This review summarizes the main progress in the precise and controllable self-assembly field in the past five years,and is mostly fo-cused on four aspects,including in-depth understanding of the assembly methods,extension of this method to two-dimensional nanostructures,utilization of this method to fabricate hierarchical structures,and the potential applications of these well-defined nanostructures.We hope not only to make a periodic systematic summary of previous studies,but also to provide some useful thinking for the future development of this field.

The Origins of Toroidal Micelles from a Liquid-crystalline Triblock Copolymer

of main observation and conclusion In this paper,we reported a systematic study on the formation mechanism of bent toroidal micelles from a triblock copolymer poly(acrylic acid)-block-(2-cinnamoyloxylethyl methacrylate)-block-poly(perfluorooctylethyl methacrylate)(PAA-b-PCEMA-b-PFMA)in the binary solvent mixture of methanol and a,a,a-trifluorotoluene(MeOH/TFT)through a heating-cooling procedure.It was found that the formation process of toroids was predominantly kinetic-controlled,and can be influenced by the preparation protocol,solvent composition and stirring rate of the solutions.The toroids were formed via a complicated morphological transition process.At high temperature,the polymer formed bilayered vesicles with bumpy surface,while upon cooling,the vesicles broke and unfolded into bumpy platelet micelles,which subsequently perforated into toroidal and cylindrical micelles upon further cooling.Besides the distinct and unique bumpy vesicle and platelet structures,the transformation mechanisms from vesicular to platelet,and toroidal micelles are also very intriguing,and may provide new insights into the interconversion of micellar morphologies.