UV-curable bismaleimides containing poly(dimethylsiloxane): Use as hydrophobic agent

Blue Light Induced Photopolymerization and Cross-Linking Kinetics of Poly(acrylamide) Hydrogels

Blue light induced photopolymerization and photo-cross-linking kinetics of acrylamide (AM), with camphorquinone/diphenyl iodonium hexafluorophosphate (CQ/DPI) as photoinitiators, were investigated. The effects of a number of parameters, including mass fraction of CQ, DPI, and AM (w_CQ, w_DPI, and w_AM) and light intensity (I), on photopolymerization efficiency and photogelation process were systematically studied by photo-differential scanning calorimetry (DSC) and photo-rheometry. Photo-DSC indicated that the maximum photopolymerization rate (R_p, max) was proportional to w_CQ^0.5, w_DPI^0.5, I^0.5, and w_AM, while Photo-Rheometry showed linear relationships between gel time t_gel and w_CQ and I, respectively, and power law relationships between t_gel and w_DPI and w_AM, respectively. In addition, both peak cross-linking rate R_c,max, and delay time t_d, which were both linearly proportional to w_CQ^0.5, w_DPI^0.5, and I^0.5, showed power law relationships with w_AM. Furthermore, exponential patterns were observed between all these factors, w_CQ, w_DPI, w_AM, and I and plateau modulus G'_∞. Combining such correlations obtained from experimental data, an empirical model was established describing the projected mechanical properties of poly(acrylamide) hydrogels from blue light initiated photopolymerization and photo-cross-linking.

UV-Curable Antismudge Coatings

Current antismudge coatings that bear nano-pools of a grafted liquid ingredient for dewetting enablement (NP-GLIDE) are cured at high temperatures, which are undesirable for application on heat-sensitive substrates. Reported herein is the development of a NP-GLIDE coating that can be photocured at room temperature. Of the various formulations that have been tested, robust coatings were obtained from one recipe consisting of a photoinitiator, a trifunctional monomer that bears three double bonds, and a graft copolymer. The last bears pendent double bonds and a poly(dimethylsiloxane) (PDMS) side chain as the antismudge agent. Coatings were prepared by casting films from a solution containing these three components and then photolyzing the resultant films. A systematic study revealed that the liquid sliding property developed on the coating at a lower cross-linking density than that required for ink to contract. Further, retaining the ability to contract ink traces after many writing and erasing cycles was the most demanding of the three antismudge tests. For our optimized formulation, only 5 min of irradiation was required to yield a transparent coating with superior antismudge properties. Moreover, irradiating selected regions and then removing, with a solvent, reagents in the nonirradiated regions can yield a surface with patterned wettability. These advantageous properties of the new photocurable coating facilitate its applications.