Synthesis and Characterization of Block Copolymers of Poly(silylene diethynylbenzen) and Poly(silylene dipropargyl aryl ether)

Poly(silylene diethynylbenzene)–b–poly(silylene dipropargyloxy diphenyl propane) copolymer (ABA-A), poly(silylene diethynylbenzene)–b–poly(silylene dipropargyloxy diphenyl ether) copolymer (ABA-O), and a contrast poly(silylene diethynylbenzene) with equivalent polymerization degree were synthesized through Grignard reactions. The structures and properties of the copolymers were investigated via hydrogen nuclear magnetic resonance, Fourier transform infrared spectroscopy, Haake torque rheometer, differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis and mechanical tests. The results show that the block copolymers possess comprehensive properties, especially good processability and good mechanical properties. The processing windows of these copolymers are wider than 58 °C. The flexural strength of the cured ABA-A copolymer reaches as high as 40.2 MPa. The degradation temperatures at 5% weight loss (T_d5) of the cured copolymers in nitrogen are all above 560 °C.

Curing behavior, thermal, and mechanical properties of N,N′-(4,4′-diphenylmethane)bismaleimide/2,2′-diallylbisphenol A/3-allyl-5,5-dimethylhydantoin resin system

The 3-allyl-5,5-dimethylhydantoin (ADMH) was synthesized and characterized by Fourier transform infrared spectroscopy, 1H-nuclear magnetic resonance (NMR), and 13C-NMR spectroscopy. Then, the ADMH was used to modify the N, N′-(4,4′-diphenylmethane)bismaleimide (BDM)/2,2′-diallylbisphenol A (DABPA) resin to obtain the BDM/DABPA/ADMH resin system (BDA). The curing behavior was investigated by non-isothermal differential scanning calorimetry and the activation energy ([Formula: see text]) was obtained by Kissinger and Ozawa models. The thermomechanical property was measured by dynamic mechanical analysis. Analysis of the data revealed the complexity of the curing reaction, which was firstly dominated by the Ene reaction of allyl and C=C double bond at low and medium temperatures and was further governed by the Diels–Alder reaction and the anionic imide oligomerization occurred at high temperatures. The results demonstrated that 1-BDA had the best thermal and mechanical properties exhibiting excellent modification effect of ADMH.

Studies on structurally different diamines and bisphenol benzoxazines

The compounds resorcinolbisbenzoxazine, quinolbisbenzoxazine, p-phenylene diaminebisbenzoxazine, and m-phenylenediaminebisbenzoxazine are prepared. The structural and thermal characterizations of the materials are done using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) and 13C NMR, and differential scanning calorimetry. Both FTIR and NMR studies reveal the presence of oxazine rings in the synthesized monomers. The curing exotherm of these bisbenzoxazines is much influenced by the nature of the aromatic unit present in the chosen compound and also on the type of the benzoxazine unit in the system. Curing kinetics is performed using Flynn–Wall–Ozawa, Vyazovkin, and Friedman methods. The apparent activation energies ( Ea-C) for the thermal curing of the synthesized monomers varied and are dependent on the nature and the position of the functional groups present in the compound. The highest Ea-C values are noted for the compounds having the functionalizations being para oriented.