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

Blue light induced photopolymerization and photo-crosslinking 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,R- 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,R-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 wAM. Furthermore, exponential patterns were observed between all these factors, w(CQ), w(DPI), w(AM), and I and plateau modulus G(infinity)'. 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.