基于聚乙烯醇的高强度可修复超分子形状记忆塑料

Mechanically Robust and Healable Poly(vinyl alcohol)-based Shape Memory Supramolecular Plastics

理想的形状记忆材料不仅要具有优异的形状记忆效应,还要具有高的力学强度和对机械损伤与形状记忆疲劳的修复能力.为制备安全可靠的形状记忆聚合物材料,本工作通过向聚乙烯醇(PVA)中引入带有吡啶基团的聚倍半硅氧烷(Py-POSS),制备了一种可修复形状记忆效应疲劳和机械损伤的高强度PVA基超分子形状记忆塑料.得益于Py-POSS与PVA之间的氢键,PVA半结晶网络的稳定性得到提高,进而显著提高了超分子塑料的强度和形状记忆能力.所制备的超分子塑料的屈服强度和模量分别可达~85.7 MPa和~6.0 GPa,形状记忆固定率和回复率都可达~99%.基于氢键的动态性,超分子塑料可在水的辅助下完全修复形状记忆的疲劳,也可修复机械损伤,展现了超分子塑料形状记忆性能优异的安全性和稳定性.

The fabrication of shape memory polymers(SMPs)with robust mechanical properties,stable shape memory performance,and the capability to heal mechanical damage and fatigue of shape memory effect is highly desired but remains challenging.In this work,mechanically robust poly(vinyl alcohol)(PVA)-based shape memory supramolecular plastics capable of healing mechanical damage and fatigue of shape memory effect are fabricated by dispersing pyridine-functionalized polyhedral oligomeric silsesquioxane(Py-POSS)in PVA matrix.Due to the hydrogen bonds among PVA and Py-POSS,the stability of the physically cross-linked PVA network are effectively enhanced.The mechanical properties of the PVA/Py-POSS_(x) supramolecular plastics,where x represents the weight ratio of Py-POSS to PVA,can be well-tailored by tailoring the mass ratio of the dispersed Py-POSS.The PVA/Py-POSS_(2.7) exhibits the highest mechanical strength,with the tensile strength and storage modulus being~85.7 MPa and~6.0 GPa,respectively.Meanwhile,the PVA/Py-POSS_(2.7) exhibits ultra-high shape memory effect with a shape recovery ratio(R_(r))and shape fixing ratio(R_(f))around~99%.Due to the reversibility of hydrogen bonds,mobility of PVA chains can be greatly improved in the presence of water,which allows the PVA/Py-POSS_(2.7) to heal the fatigued shape memory function.The total recovery ratio(R_(r,tot))of the PVA/PyPOSS_(2.7) is maintained above 93%after 90 folding/recovery cycles by conducting the healing step in a 90%RH environment after every 10 shape memory cycles.Based on the same mechanism,the mechanical damage on the PVA/Py-POSS_(2.7) can also be fully healed with the assistance of water.The healed PVA/Py-POSS_(2.7) exhibits the same shape memory function as the original sample does.The combination of ultra-high mechanical strength and healability enables the PVA/Py-POSS_(2.7) to maintain its excellent shape memory performance during long time and repeated usage.Integrating nanofillers that have reversible interactions with polymer materials provide an effective avenue for fabricating high-performance SMPs with enhanced reliability and prolonged service time.