Thermal Properties and Self-Assembly Behaviors of Triblock Copolymers Consisting of PEG Segment and Acrylamide-Based Block Bearing Alkyl Side Chains Prepared by RAFT Method

A new series of hybrid triblock copolymers (TBCs) based on hard–soft–hard segments are synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization using a macroinitiator poly­(ethylene glycol) (PEG) macromolecular chain transfer agent (macro-CTA) and monomer p-dodecylphenyl-N-acrylamide (DOPAM). The resulting TBCs are characterized and evaluated by 1H NMR, gel permeation chromatography, and differential scanning calorimetry. Kinetic studies on triblock copolymerization indicated the controlled/living characteristic of RAFT polymerization with good distribution of molecular weight (M w/M n ≤ 1.39). All TBCs exhibited two melting temperatures (T m) at 50 and 240 °C unlike PEG macro-CTA, which revealed a single T m at 50 °C. However, TBC-4 and TBC-5 showed strong T m (PDOPAM) peaks compared to TBC-1, TBC-2, and TBC-3, mainly due to the increase in the volume fraction of PDOPAM. Morphologies of TBCs are studied by atomic force microscopy and grazing incidence small-angle X-ray scattering. TBCs (TBC-2, TBC-4, and TBC-5) with different blocks ratios (f PDOPAM ≠ f PEG) formed cylindrical phases, in particular TBC-5 containing a higher PDOPAM ratio (72%) generated a highly ordered cylindrical nanostructure. Contrastingly, TBC-3 with nearly the same length of PDOPAM (49%) and PEG (51%) self-assembled into the lamellar phase.