After ageing, the PMSQ gels were first washed in methanol (Sinopharm Chemical Reagent Co., Ltd). The methanol was exchanged with fresh methanol three times every 12 hours. The gels were then washed in 2-propanol (Sinopharm Chemical Reagent Co., Ltd) three times every 12 hours to remove CTAC. Subsequently, the PMSQ gels were chemically modified by 2-propanol (Sinopharm Chemical Reagent Co., Ltd)/HMDSO (Hangzhou Guibao Chemical Co., Ltd, China)/HCL (36.4%, Sinopharm Chemical Reagent Co., Ltd) solutions. In this study, 200 ml 2-propanol was used as the solvent. Different amounts of HMDSO were added to the solution. The HMDSO : HCL molar ratio was kept constant at 5 : 4.
After the surface modification process, the PMSQ gels were washed in HMDSO solution exchanged with fresh solution three times every 12 hours. During the drying process, HMDSO was slowly removed by evaporation at room temperature for 1 d. After drying, the aerogels were heated at 90 °C for 2 h and 160 °C for another 2 h to allow the further spring-back of the gel network. Modified-7 could not spring back further after heating at 160 °C. Thus, Modified-7 (48 mg cm−3) was further heated at 300 °C for 1 h to allow further spring-back of the gel network.
After the surface modification process, the PMSQ gels were washed in HMDSO solution exchanged with fresh solution three times every 12 hours. During the drying process, HMDSO was slowly removed by evaporation at room temperature for 1 d. After drying, the aerogels were heated at 90 °C for 2 h and 160 °C for another 2 h to allow the further spring-back of the gel network. Modified-7 could not spring back further after heating at 160 °C. Thus, Modified-7 (48 mg cm−3) was further heated at 300 °C for 1 h to allow further spring-back of the gel network.