The shrinkage of UV-curable polymers is directly related to the structural changes in the monomer behavior of the system. The issue of shrinkage in these systems can be mitigated by leveraging the dynamic behavior of disulfide bonds. However, it remains unclear how light induction affects the contraction of the system through processes such as bond cleavage, migration, and recombination of disulfide bonds. In this study, we modified the polyurethane core of a UV-curable system by incorporating three different topologies of disulfide bonds. We examined the impact of these different arrangements and their dynamic adjustment on reducing shrinkage using scanning electron microscopy, shrinkage rate tests, and theoretical analysis based on the Gauss-type radial distribution probability density function. Our findings show that the modified sample exhibited lower curing shrinkage and a smoother surface compared to unmodified polyurethane. Specifically, while the shrinkage rate before modification (PU) was 5.16%, after modification (DSBT-PU, DSBP-PU, DSBE-PU) it decreased to 1.24% for DSBT-PU, 0.67% for DSBP-PU, and 0.95% for DSBE-PU. We also observed that longer chain lengths in disulfide-containing fragments aided in dynamically adjusting the system structure. However, the increase in the molecular fragment length makes it more difficult to migrate dynamic disulfide bonds. Furthermore, our synthetic sample demonstrated high transmittance levels, exceeding 98%. Additionally, we conducted comprehensive examinations including testing 180° peel strength, differential scanning calorimetry, thermogravimetric analysis, tensile characteristics, and transmittance properties, among others. This work not only sheds light on how dynamic bonds influence system structure but also holds practical implications for applications in liquid optical clear adhesive (LOCA) and unique pressure-sensitive adhesives.
Chang-an Xu,Wenzi Liang,Xiankun Wu,Enxiang Jiao,Mangeng Lu,Kun Wu,Xiaopeng Hao,Jun Shi
At present, the energy crisis is becoming increasingly outstanding, and the expanding market of pressure sensitive adhesives (PSAs) puts forward higher requirements for biomass materials. Vanillin comes from biomass raw materials, and it has been widely used in related research fields. So far, there are few reports on the preparation of novel monomers containing Schiff base structure from silicone and vanillin. In this work, vanillin reacts with methacrylic anhydride to prepare monomers with double bond structure, and furthermore a fresh type of silicone/vanillin monomer is prepared by aldehyde-amine condensation reaction . Finally, the novel monomer is introduced into polyurethane matrix, and a series of silicone/vanillin-based PSAs are prepared under UV conditions. The results show that the introduction of silicone/vanillin monomer can improve the residual carbon rate of PSAs, and the residual carbon rate of PUPG-C is as high as 12 wt%. Moreover, by comparison to the control group PUPG-0, the ball number, 180° peel strength and shear strength of PUPG-A are increased by 120.0 %, 215.0 % and 49.8 %, respectively. It is worth noting that the 180° peel strength of PSAs on functionalized glass has been strengthened, which greatly promotes the application of PSAs on functionalized glass. In short, this work provides a simple, versatile and extensible method for designing PSAs with silicone/vanillin structure in the future.
危险品化学品经营许可证（带存储）