Preparation of Transparent and Flexible Shape Memory Polybenzoxazine Film through Chemical Structure Manipulation and Hydrogen Bonding Control

Polybenzoxazines consisting of chemical structures that differ from conventional polybenzoxazines were obtained at relatively lower temperature with the aid of Lewis acids. It is confirmed by FTIR spectra that the new polybenzoxazines mainly consist of arylamine Mannich-type linkage other than phenolic Mannich-type linkage in conventional polybenzoxazines. Owing to the unique chemical structures, the arylamine Mannich polybenzoxazines possess more weak -OH center dot center dot center dot pi hydrogen bonding but less strong and rigid chelated hydrogen bonding. As a result of the special chemical structures and hydrogen bonding distribution, the arylamine Mannich polybenzoxazines possess many unique properties. For example, they are more flexible. Tensile tests show that the arylamine Mannich polybenzoxazines could be stronger and tougher than phenolic Mannich polybenzoxazine. The highest tensile strength increases 83% while elongation at break value increases 115% for 002P180 (arylamine Mannich polybenzoxazine) compared with PBA-a200 (phenolic Mannich polybenzoxazine). The better toughness is also confirmed by cross-sectional SEM images. More interestingly, the arylamine Mannich polybenzoxazines possess shape memory effect (SME), the deformation could be rapidly recovered, and the recovery ratio is higher than 95% within 2 min for polybenzoxazines catalyzed by PCl5. The T(g)s increase with elevating curing temperatures and vary from 50 to 162 degrees C, covering the range of middle to high transition temperature shape memory polymers (SMPs). It is very convenient that the properties of the polymer can be simply tailored by varying curing temperatures.