Topology Reliable LCST‐Type Behavior of ABA Triblock Polymer and Influence on Water Condensation and Crystallization

Abstract

As a kind of smart material, thermoresponsive hydrogels are widely investigated and applied in many fields. Due to the limitation of the freezing temperature of the water, it is a challenge to further broaden their sol–gel transition temperature (Tgel) range, especially below 0 °C. Herein, the lower critical solution temperature type of amphiphilic ABA triblock copolymers, synthesized via two‐step reversible addition‐fragmentation chain transfer (RAFT) polymerization is demonstrated. The hydrophilic A‐block and the hydrophobic B‐block are composed of poly(N,N‐dimethylacrylamide) (PDMAA) and poly(diacetone acrylamide) (PDAAM), respectively. The degree of polymerization (DP) of both A‐block and B‐block shows a significant influence on the Tgel of triblock copolymer dispersion. By changing the length of these two blocks or physically blending these copolymers dispersions, the Tgel can be well adjusted in a temperature range from 45 to −10 °C. Moreover, When the Tgel is higher than 4 °C, the triblock copolymer coatings show a good anti‐fogging property. And when the Tgel is around or lower than the freezing temperature of the water, aqueous dispersions of the triblock copolymer have an ice recrystallization inhibition activity, resulting in the decrease of average maximum grain size (MLGS) of ice crystal.

In situ insight into the self-assembly evolution of ABA-type block copolymers in water during the gelation process using infrared spectroscopy and near-infrared spectroscopy

“…That is adjusting the DP of the hydrophobic block can more precisely control the T gel of copolymer solution than adjusting the DP of the hydrophilic block. 33…”

“…By controlling the chain length of hydrophilic and hydrophobic blocks, the transition temperature ( T gel ) could be adjusted, even to a temperature lower than the freezing point of water. 33 Following these results, it can be assumed that the exchange of hydrogen bonding within polymer chains, as well as the interaction between polymer and water, would give crucial effects on the structure design of such materials.…”