Synthesis and Self-Assembly of Polystyrene and Poly(hydroxy styrene)-Based Amphiphilic Bottlebrush Block Copolymers with Featuring Structural Colors

Abstract

Self-assembly of amphiphilic bottlebrush block copolymers (AmBBCP) has attracted tremendous attention due to the control of their morphology in nanoscopic domains. Hydrophilic group in the AmBBCP can take part in hydrogen bonding (H-bonding) with functional additives. The unique properties facilitate the precise control for shape and size of nanostructures in bulk as well as solution. In particular, the AmBBCPs with ultrahigh molecular weights (UHMW) are potentially relevant as photonic crystals, which are comprised of well-controlled lamellae. However, only a few AmBBCPs with UHMWs have been similarly investigated. Their self-assembly behavior is relatively unveiled. To improve understanding of the AmBBCP-based phase separation in ‘polymer science’ field, I chose poly(styrene-block-hydroxystyrene) as a model of the AmBBCPs. Chapter 1 covers key concepts including recent advances in structural features, synthetic method, and controlled self-assembly of amphiphilic bottlebrush polymers. Chapter 2 introduces an efficiently synthetic grafting-through strategy. Before preparing AmBBCPs, well-defined BBCPs with UHMWs are established by first. Macromonomers containing polystyrene and poly(4-tert-butoxystyrene) were synthesized by living anionic polymerization, termination, and amidation. Precise synthesis of the BBCPs, poly[(norbornene-graft-styrene)-block-(norbornene-graft-tert-butoxystyrene], were achieved by sequential ring-opening metathesis polymerization (ROMP) of two macromonomers. Effect of UHMWs of the BBCP was demonstrated by fabrication of photonic crystals. Chapter 3 explores a simple strategy to systematically control phases transition of an amphiphilic bottlebrush block copolymer (AmBBCP), poly[(norbornene-graft-styrene)-block-(norbornene-graft-hydroxystyrene)], with polymeric additives, such as poly(ethylene glycol) methyl ether (mPEG), poly(2-vinylpyridine) (P2VP) and poly(methyl methacrylate) (PMMA). The relationship between H-bonding and phase transition behavior were compared. The mPEG efficiently modulated refractive index, domain sizes, phase transition along with photonic characteristics. Chapter 4 discusses volatile organic compounds (VOC)-induced reconstruction of lamellar morphology. The lamellar structures are formed by self-assembly of AmBBCP/mPEG blends through dioxane vapor annealing. Benzene and toluene selectively swell polystyrene domain, whereas acetone and acetaldehyde are favorable for poly(hydroxystyrene)/mPEG blends domain. These solvents take effect on domain sizes and refractive index, and thereby provide the VOC detector to show different structural coloration.