TY - JOUR

T1 - Dual-Cure Coatings

T2 - Spiroorthoesters as Volume-Controlling Additives in Thiol–Ene Reactions

AU - Marx, Philipp

AU - Romano, Angelo

AU - Fischer, Roland

AU - Roppolo, Ignazio

AU - Sangermano, Marco

AU - Wiesbrock, Frank

N1 - Publisher Copyright: © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

PY - 2019/4

Y1 - 2019/4

N2 - Most thiol–ene systems exhibit shrinkage during cross-linking, potentially resulting in micro-cracks and delamination. Oligocyclic monomers like spiroorthoesters (SOEs), on the contrary, show expansion during the ring-opening polymerization. In this communication, a photocurable thiol–ene system composed of a trifunctional thiol, a bisfunctional allyl-bisphenol A compound, and an SOE compound bearing one olefin function shows expansion in the range from −3.07 to +1.70 vol% if the SOE content is increased from 0–30 wt%. Network formation can be accomplished under visible light if a radical as well as a cationic photoinitiator (dual-cure mechanism) and a sensitizer are used. The elasticity of the cured resin increases upon the addition of the SOE; correspondingly, the glass-transition temperature shows a (minor) decrease from 16 to 3 °C. A tailor-made combination of the allyl-bisphenol A compound (90 wt%) and the SOE (10 wt%) yields networks that are volume-neutral during curing.

AB - Most thiol–ene systems exhibit shrinkage during cross-linking, potentially resulting in micro-cracks and delamination. Oligocyclic monomers like spiroorthoesters (SOEs), on the contrary, show expansion during the ring-opening polymerization. In this communication, a photocurable thiol–ene system composed of a trifunctional thiol, a bisfunctional allyl-bisphenol A compound, and an SOE compound bearing one olefin function shows expansion in the range from −3.07 to +1.70 vol% if the SOE content is increased from 0–30 wt%. Network formation can be accomplished under visible light if a radical as well as a cationic photoinitiator (dual-cure mechanism) and a sensitizer are used. The elasticity of the cured resin increases upon the addition of the SOE; correspondingly, the glass-transition temperature shows a (minor) decrease from 16 to 3 °C. A tailor-made combination of the allyl-bisphenol A compound (90 wt%) and the SOE (10 wt%) yields networks that are volume-neutral during curing.

KW - dual-cure mechanisms

KW - spiroorthoesters

KW - thiol–ene reactions

KW - thiol–ene resins

KW - UV-mediated curing

KW - volumetric expansion

UR - http://www.scopus.com/inward/record.url?scp=85060189625&partnerID=8YFLogxK

U2 - 10.1002/mame.201800627

DO - 10.1002/mame.201800627

M3 - Article

AN - SCOPUS:85060189625

VL - 304.2019

JO - Macromolecular materials and engineering

JF - Macromolecular materials and engineering

SN - 1438-7492

IS - 4

M1 - 1800627

ER -