Light-Directed Organization of Polymer Materials from Photoreactive Formulations

Abstract

This perspective presents a recently developed approach to organize polymer and polymer composite materials through a new form of light-directed organization of photoreactive polymeric media. Under suitable conditions, such media will interact with light, in a mutual dynamic process, that results in the spontaneous organization of both the input light field and, importantly, the polymer media. New material structures can be created in free-radical-initiated media, polymer blends and polymer−solvent mixtures, as well as possibly more complex, multicomponent formulations. An overview of the underlying principles and chemical phenomena and exemplary material structures are presented. Materials produced using this new processing approach can be used as functional coatings, textured surfaces, and membranes, as well as a host of other applications via selection of polymer composition. Key open questions and areas for further inquiry and advancement are presented. Coupling the dynamics of light pattern formation processes to photoreactive matter is a promising new approach to the organization of materials for a range of critical applications and reveals interesting nonlinear dynamic phenomena in the organization of materials.

Simulations of Structure and Morphology in Photoreactive Polymer Blends under Multibeam Irradiation

“…Directing the organization of polymer blends into new structures and morphologies is an important approach toward the creation of soft materials with functional properties. 1 Specifically, producing polymer materials from reactive blends enables the concurrent assembly of complex structures over the course of polymerization. The reaction-induced increase in molecular weight can render the blend thermodynamically immiscible, thereby driving polymerization-induced phase separation (PIPS).…”

“…Most recently, photoreactive polymer blends have been organized using single arrays of optical beams transmitted through photoreactive monomer blend media that are sensitized to undergo photoinitiation at the optical beam’s particular wavelength. 1 , 11 The optical beams are observed to undergo a self-focusing nonlinearity, associated with a photochemically induced increase in refractive index, which counters the optical beam’s natural divergence. 12 − 17 The dynamic balance of self-focusing and divergence leads to self-trapped beams, which propagate divergence-free, or beams with reduced divergence transmitted through the polymer blend medium.…”

“…As a result, the polymer blend morphology evolves via spatially controlled phase separation uniformly along its depth, with one polymer component in the regions of the optical beams (i.e., regions of irradiation) and the other in the nonirradiated regions surrounding it, effectively organizing the blend into the same pattern as the ensemble of transmitted optical beams. 1,11,15 The structure and morphology of the blend can then be controlled via light intensity, 15 optical beam size and interspacing in an array, 18 formulation composition and component molecular weight, 19−21 and component volume fractions. 19 To advance the complexity of the organized structures, there is interest in examining structure formation in polymer blend media irradiated with multiple, nonparallel arrays of optical beams.…”

Multidirectional Polymer Waveguide Lattices for Enhanced Ultrawide-Angle Light Capture in Silicon Solar Cells

“…This is in good agreement with measurements of degrees of phase separation in previous work. 29 , 40 As the collection ranges were not significantly different between the two CQ concentrations, the collection angles could not be used to back-calculate any difference in the degrees of phase separation of the blends when using different CQ amounts. It is possible that differences observed in subsequent solar cell performance (to be discussed in the next section) are a result more so of internal waveguide morphology.…”

Superhydrophobic Polymer Composite Surfaces Developed via Photopolymerization

“…1,2,10 To address the challenges outlined above, here we report an approach based on photopolymerization-induced phase separation (referred to herein as PhIPS) in photopolymer− NP formulations to develop surface-patterned polymer composite superhydrophobic materials. PhIPS is a unique method for the directed organization of materials, 24 which we leverage herein to uniquely organize structured materials simultaneously from two different components, that is, the polymer and the NPs without the use of solvents, in thin casted films. By inducing PhIPS in a casted thin film of the formulation, the photopolymer evolves into a substrate with periodically spaced "bumps" in the regions of elevated curing rate, and the phase separation of the NPs is directed to the top surface of the polymer substrate, thereby producing a dense, yet thin, NP overlayer.…”