Photopolymerization-induced phase separation (PhIPS) is a promising technique to generate coatings with controllable properties. Controlled phase separation has demonstrated that certain polymer morphologies can enhance mechanical properties (e.g., toughness) or tunable surface characteristics such as gloss and roughness. PhIPS is an attractive technique to create morphologies, as it offers direct control over polymerization kinetics, which directly impacts polymer network formation and phase separation. The surface morphology resulting from phase separation depends on several parameters, including the competition between thermodynamically-driven phase separation, the physical changes associated with monomer conversion, irradiation conditions, photoinitiator type/concentration, formulation composition, and film thickness. Advantages of working with a hybrid system to induce low-gloss UV-curable coatings, beyond the self-roughening create by phase-separation is the increased conversion of acrylates and epoxies, increased hardness and reduced use of conventional matting agents. Furthermore, PhIPS allows production of micro-structures in a single step and the rapid formation of rough surfaces at multiple length scales in a solvent-free environment. This work describes PhIPS of free-radical/cationic hybrid systems. The phase separation and demixing of incompatible macromolecular liquids create microstructural phase heterogeneity and microphase separation of the different components. The decrease in gloss can be controlled by different size scales of phase-separated domains to achieve a surface roughness that scatters light irregularly in several directions. Phase separation morphologies, polymerization kinetics, final properties (e.g. gloss and hardness) are studied depending on the ratio of the acrylate/epoxy mixture and can be controlled by the photoinitiator content.

Influence of photoinitiator content on phase separation and microstructure of free-radical/cationic hybrid system and its application for low-gloss UV-curable coatings

ACS Spring Meeting 2021

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