Amorphous Shape-Memory Polymers with End-Capped Urethane Cross-Linking

The patent segments the cross-linking process into two distinct stages: first physical cross-linking to establish solvent resistance and basic shape-memory properties, then chemical cross-linking of end-capping units to enhance processability. This segmentation allows each cross-linking mechanism to fulfill different functional requirements without compromising the other.

The patent applies preliminary physical cross-linking before chemical cross-linking to establish the fundamental shape-memory network. This preliminary action creates a stable base that enables subsequent chemical modification of end-capping units without disrupting the core cross-linked structure, thereby improving processability while maintaining solvent resistance.

The patent applies local quality by restricting chemical cross-linking to only the end-capping units of the polymer chains, while the main polymer backbone remains physically cross-linked. This localized chemical modification provides enhanced processability at the chain ends without compromising the solvent resistance provided by the bulk physical cross-linked network.

The patent creates a composite cross-linked structure combining physical cross-links in the polymer backbone with chemical cross-links at the end-capping units. This composite approach integrates the solvent resistance of physical cross-linking with the processability benefits of chemical cross-linking, achieving both properties simultaneously.