Coincident augmentation and alignment of lamellar stacking structures for rapid fabrication of solid-state polymer photonic crystal films

Background

Microphase Separation from block copolymers can form ordered microstructures in different dimensionalities by controlling the chemical nature, degree of polymerization, as well as volume fractions of the constituent block. The block copolymer photonic crystal (PC) gels with ordered microstructures can be tailored to manipulate photonic bandgaps and light propagation characteristics for sensing various stimuli. To expand applications, the fabrication of the block copolymer PCs in the solid state is necessary. However, this challenge requires the synthesis of ultrahigh-molecular-weight (> 1000 kg/mol) copolymers to increase the periodicity and control microstructural orientation.

Methods

The generation of PC films in a solid state is carried out using ternary block copolymer supramolecules, poly(methyl methacrylate)-block-poly(2-vinyl pyridine) (PMMA-b-P2VP) cooperated with mesogens of cholesteryl hemisuccinate (CholHS) and poly(methyl methacrylate) homopolymer (hPMMA).

Significant findings

Without time-consuming multiple steps for the augmented periodicity and microstructural alignment, control over the photonic bandgap covering the entire visible spectrum, facilitated by the arrangement of alternating high- and low-refractive-index stacking layers, can be carried out through these innovative co-assembled supramolecules. The photonic bandgap of the PC can be simply adjusted by the structural periodicity through manipulating the quantities of mesogens due to the stretching of the P2VP block chain by hydrogen bonding interaction. Also, the included liquid crystalline mesogen can induce parallel alignment of the lamellae such that large-area block copolymer PCs in the solid state can be rapidly fabricated, promising in sensing, display, and anti-counterfeit applications due to the ease of functionalized P2VP chains.