Synthesis of core cross-linked star polystyrene with functional end groups and self-assemblies templated by breath figures

In this paper, we report the synthesis of core cross-linked star (CCS) polymers with functional end groups for self-assembled films, which show monolayer, bilayer, or multilayer structures, depending on arm numbers, arm length, and end groups. The stars were synthesized via the “arm-first” method using a linear polystyrene as an atom transfer radical polymerization (ATRP) macroinitiator that is end-capped with a hydrolysable cyclic lactone end group. The relatively hydrophobic cyclic group can be converted into hydrophilic neutralized carboxyl and hydroxyl groups via alkaline hydrolysis and acidification processes. The polymers were characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (NMR). The conversion of the macroinitiators was evaluated by fitting the GPC curves. We found that the star polymers are easier to form ordered honeycomb films than the corresponding linear analogue. Moreover, the end groups of the stars show an obvious impact on the film surface structures only at relatively low concentration. More importantly, stars with lower arm numbers or longer arms tend to form bilayer or multilayer structured films. On the other hand, stars with hydrophilic end groups are much easier to form bilayer or multilayer structured films. Considering the importance of mono- or multilayer structures of honeycomb films in various fields such as separation membranes, templating materials, and optical materials, these results will be valuable in tailoring film-forming materials toward films with designed structures.