Preparation And Properties Of Sulfonated Polybenzoxazine Proton Exchange Composite Membrane

Sulfonated polybenzoxazine membrane is a new proton exchange membrane,which has excellent alcohol-resistance,excellent dimensional stability,good heat-resistance,and low prices.It has a broad development prospects in the field of proton exchange membrane.However,the membrane has polybenzoxazine inherent drawback which is difficult to form film and poor toughness.In order to broaden polybenzoxazine application in the field of proton exchange membrane,it needs to be toughened.Thermoplastic polymers toughening polybenzoxazine is a commonly method.Poly(vinyl alcohol)is an excellent thermoplastic polymer,which not only has good film-forming properties and acid-alkaliresistance,but also has low prices.In this paper,poly(vinyl alcohol)is used for preparing sulfonated polybenzoxazine/poly(vinyl alcohol)(SPBZ/PVA)composite membranes.Poly(vinyl alcohol)is sulfonated to prepare sulfonated polybenzoxazine/sulfonated poly(vinyl alcohol)(SPBZ/SPVA)composite membranes.The main contents and results are shown as follows:1.The sulfonated benzoxazine monomer(SBZ)was synthesized via Mannich reaction and acidizing reaction using sodium 4-hydroxybenzenesulfonate,paraformaldehyde,and 4,4'-diaminodiphenylmethane as raw materials.The structure of the SBZ was characterized by Fourier transform infrared(FTIR)spectroscopy.The SPBZ/SPVA composite membranes were prepared by solution casting method.The mechanical properties,the film-forming ability,the proton conductivity,and the methanol permeability of the composited membranes were studied.Our results show that when the PVA content was 10%,the elongation at break of the composite membranes was 2.78%which was 44.8%higher than the pure SPBZ membrane at the dry state.The elongation at break was 11.78%which was 42.8%higher than the pure SPBZ membrane at the wet state.The proton conductivity was 13.3 mS/cm at 80?.The methanol permeability was 1.51×10-7 cm2/s and slightly increased comparing with the pure SPBZ membrane.The dimensional stability.The oxidation stability,the heat-resistance,and the thermal stability is excellent.2.Sulfonated poly(vinyl alcohol)(SPVA)was synthesized via esterification reaction using PVA and 98wt%sulfuric acid as raw materials.The structure of the SPVA was characterized by FTIR.The SPBZ/SPVA composite membranes were prepared by solution casting method.The mechanical property,the proton conductivity,and the methanol permeability of the composite membranes were studied.Our results show that when the SPVA content was 10%,the proton conductivity was 16.7 mS/cm at 80 ? which was 25.6%higher than SPBZ/PVA-10 membrane(13.3 mS/cm).The methanol permeability was 1.38×10-7cm2/s and slight increased comparing with the pure SPBZ membrane.The elongation at break of the composite membranes was 9.00%which was 24.5%higher than the pure SPBZ membrane(7.23%)at the wet state.The dimensional stability,the oxidation stability,and the thermal stability was excellent.