1. Add 0.5 g boric acid into 10 mL methanol and continuously stirred for 1 h.
2. 10 g of PDMS (hydroxyl terminated) and above solution were vigorously mixed together for 2 h.
3. The product was poured into a Petri dish and kept in a fume hood for 2 h to evaporate most of the ethanol.  Then the product was kept in vacuum at room temperature for 12 h to remove residual methanol.