Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE The molecular weights determined by end-group analysis, theoretical molecular weights calculated from hydroxyl number and experimental GPC data, the NCO content before and after preparation, the DSC curves of macro-crosslinkers, the TGA curves of copolymers with different macro-crosslinkers, the stress–strain curves, the change of stress or strain in relaxation and recovery tests, and the 180° peel strength of palatized PH series, and the stress–strain curves before and after aging tests.

ABSTRACT
To achieve a balance of low modulus, high recovery, and strong adhesion in pressure-sensitive adhesives (PSAs) of flexible displays, a series of crosslinkable oligomers with varied structures and molecular weights are synthesized and subsequently incorporated into acrylate copolymers as macro-crosslinkers. The structure of the macro-crosslinkers is characterized by Fourier transform infrared (FT-IR), nuclear magnetic resonance spectroscopy (1H NMR), and gel permeation chromatography (GPC). The effects of the macro-crosslinkers' structure and molecular weight on the properties of copolymers are systematically investigated by differential scanning calorimetry (DSC), rheometer, and universal testing machine. The macro-crosslinkers enhance the chain mobility while maintaining the integrity of the crosslinking network, leading to a more flexible network with a combination of strong cohesion and high chain mobility. Compared to HDDA-crosslinked copolymers, the copolymers with macro-crosslinkers exhibit a lower modulus, superior elongation, and enhanced stress relaxation, while maintaining comparable strain recovery and cyclic stability. For instance, P-cPPG1k exhibits a 26% reduction in modulus, a 60% increase in elongation at break compared to P-HDDA, with an elastic recovery rate maintained over 92% at 200% strain. Moreover, P-cPPG1k exhibits adhesive performance superior to commercial flexible display PSAs, underscoring the practical potential of this strategy.