Synthesis and characterization of Poly(ethylene glycol)-based segmented ionenes block copolymer with aliphatic or DABCO hard segments

A series of poly(ethylene glycol) (PEG)-based segmented block copolymers were synthesized with two structurally different hard segments, linear and heterocyclic aliphatic amines. Ionenes were synthesized via a modified Menshutkin reaction with three different weight fractions of hard domains (amine rich segment) and soft domains (PEG oligomers). TGA results show that both aliphatic and DABCO-based ionenes were thermally stable up to 250 degrees C. DSC and XRD data indicate that increasing the weight fraction of the soft segment from 25 wt % to 50 wt% triggered better chain packing of the PEG soft segment for both hard segments. Also, the DABCO-based ionenes displayed the highest PEG crystallite purity at 50 wt% of soft segment. The segmented ionenes exhibited high strain elongation percentages at elevated temperatures (i.e., above the PEG melting temperature). The mechanical properties of ionenes changed by varying the nature and the weight fractions of soft and hard domains. DMA analysis concluded that DABCO-based ionenes possess superior elastomeric behavior by having a wider rubbery plateau and higher rubbery plateau storage modulus compared to aliphatic analogs at all weight fractions potentially due to better microphase separation and ionic aggregation. DMA and AFM confirmed that the 25 wt% soft segment ionenes had a relatively higher degree of microphase separation among the other weight fractions.