Microstructural transition of poly(vinyl alcohol)-based aerogels in the presence of interpolymer complexes

Interpolymer interactions play a vital role of determining the microstructure and properties of polymer aerogels. In terms of poly(vinyl alcohol) (PVA) aerogels, the conformation and behaviour of polymer chains in semidilute aqueous solutions make considerable contribution to the evolution of polymer matrixes during preparation. In this work, we investigated the microstructure of a group of PVA-based aerogels from the view of interactions between polymer chains. In PVA/poly(ethylene oxide) (PEO) aerogels, disordered microstructures were formed with the increase in PEO amount, owing to the existence of weak hydrogen bonds and some existing crystalline domains of PVA and PEO. PVA/poly(acrylic acid) (PAA) samples, presented straight stripe-shaped structures, because of the strong interactions between PVA and PAA. In PVA/carboxyl methyl chitosan (CM-CTS) aerogels, high density of stripe microstructures were observed, due to the rigid conformation of CM-CTS in water and few hydrogen bonds existed between PVA and CM-CTS. PVA/PAA aerogels possess compressive strength as high as 0.94 MPa. The porosity of the PVA/PEO aerogel reached 98.6%. Factors such as chain length and pH value of the precursor solutions on the microstructure of aerogels were also investigated. A possible forming mechanism was put forward from the view of interpolymer interactions, accordingly. Such way of tuning the microstructure of PVA-based aerogels may provide a new understanding with respect to the microstructure of polymer aerogels and pave new ways for the practical use of this versatile light material.