Surface creasing in swelling polymer gels is commonly attributed to compressive strain or interlayer mismatch, yet its general control remains unclear. Here we show that solvent polymerization degree Ns provides an independent control parameter for crease onset in surface-bound polydimethylsiloxane gels swollen by silicone oils. Despite nearly identical swelling kinetics and through-thickness solvent concentration profiles, we observe a transition from creased to stable surfaces with increasing Ns. A theory coupling swelling thermodynamics and mechanical stability reveals that polymeric solvents reduce the mixing entropy and thereby modify the osmotic pressure, allowing Ns to tune separately the equilibrium swelling and the crease threshold. This framework captures the stability boundary across solvent polymerization degree and network elasticity. These results identify polymeric solvents as active thermodynamic-mechanical regulators of swelling-induced surface.
@article{arxiv.2604.20299,
title = {Polymeric Solvents Control Swelling-Induced Surface Creasing},
author = {Zechao Jiang and Zhaoyu Ding and Shaohua Yang and Ye Xu and Dongshi Guan and Abdelhamid Maali and Joshua D Mcgraw and Thomas Salez and Zaicheng Zhang and Xingkun Man},
journal= {arXiv preprint arXiv:2604.20299},
year = {2026}
}