Stabilizing the Microphase Separation of Block Copolymers by Controlled Photo‐crosslinking

Abstract

Photo‐crosslinkable material is produced via self‐assembly of poly(methyl methacrylate)‐block‐poly(n‐butyl acrylate) (PMMA‐b‐PBA) block copolymers, in which the MMA block is decorated with coumarin moieties. The block copolymer is synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. Atomic force microscopy (AFM) reveals microphase separation into nanodomains of controlled and regular morphology. The local elastic modulus of different nanodomains is determined using the PeakForce Quantitative Nano‐Mechanics (PFQNM) mode of AFM. The global modulus, as determined by mechanical spectroscopy, agrees well with the local values. The crosslinking of the block copolymer, via photodimerization of the incorporated coumarin moieties using UV light, is traced by UV–vis absorption measurements and resulted in an increase of the global elastic modulus. The crosslinking reaction proceeding in the solid state is surprisingly effective and stabilizes the morphology to such an extent that equilibrium phase separation, as targeted by annealing, is effectively suppressed.

pH/UV Responsive Polymeric Micelles Based on Coumarin to Tune Emulsification/Solidification Performance

“…The reversible photo‐cross and de‐cross‐linking process of coumarin has been well known in the early 20th century . To trace the reversible behaviors of photo‐cross‐linking, Figure c and 3d showed the diameter change of micelles under UV irradiation with different wavelengths during the self‐assembly process.…”

Nanostructured Thin Films of Moderately Functionalized PMMA‐b‐PS

“…Particularly, we report on the crucial preliminary steps in order to use these BCPs for (bio)molecular patterned immobilization, that is, their self‐assembly behavior and the stability in aqueous medium of the thin films made thereof. This study is also relevant as, despite a few reports having already showcased this possibility in the frame of BCP film stabilization by crosslinking, we often encountered skepticism as to whether the incorporation of a small amount of comonomer would disrupt the phase separation ability of BCPs. Our present aim is to demonstrate the feasibility and breadth of this strategy.…”

Fluorescent Dyes Used in Polymer Carriers as Imaging Agents in Anticancer Therapy

“…Photodimerization of coumarin derivatives units proceeded faster in lower Tg (glass transition temperature) polymers [244]. The Tg describes the mobility of a main copolymer chain and it is an essential factor to affect the rate of photodimerization [245][246][247]. The intramolecular photodimerization is preferred in high Tg polymers because of the low mobility of a main chain, thus the higher conversion to dimers i.e.,, larger number of cross-linking points [247,248].…”

“…The Tg describes the mobility of a main copolymer chain and it is an essential factor to affect the rate of photodimerization [245][246][247]. The intramolecular photodimerization is preferred in high Tg polymers because of the low mobility of a main chain, thus the higher conversion to dimers i.e.,, larger number of cross-linking points [247,248]. Instead, in low Tg polymers (used e.g., 2-ethyhexyl methacrylate or n-butyl acrylate monomers) the intermolecular photodimerization competed with the intramolecular photodimerization and a performed network is loosely cross-linked.…”