After confirmation of monomer consumption by 1 H NMR, the polymerization was terminated by addition of ethyl isonipecotate at 50 °C for 4 h. The solvent was removed under reduced pressure. The polymer was transferred into a dialysis bag (MWCO 1 kDa, cellulose acetate, Spektrum TM , Rancho Dominguez, CA, USA) and dialysed against deionized water for two days with several water changes. Afterwards, the solution was recovered from the bag and lyophilized.