Steric hindrance effect on thermo-responsive behaviors of well-defined water-soluble semi-rigid polymers

Abstract

Three series of water-soluble semi-rigid thermo-responsive polymers with well-defined molecular weights based on mesogen-jacketed liquid crystal polymers, poly [bis(N-(2-hydroxypropyl) pyrrolidoneand poly[bis(N-hydroxypropyl pyrrolidone) 2-vinylterephthalate] (PHPPVTA) have been synthesized via reversible addition-fragmentation chain transfer polymerization. The steric hindrance effects on liquid crystalline property and thermo-responsive behaviors of semi-rigid water-soluble polymers (P(2-HPPVTA), P(1-M-2-HEPVTA), and PHPPVTA) were carefully investigated. From molecular structure, the steric hindrance of P(1-M-2-HEPVTA) is stronger than that of P(2-HPPVTA). Polarized light microscope and onedimensional wide-angle X-ray diffraction revealed that both the P(2-HPPVTA) and P(1-M-2-HEPVTA) display a columnar nematic phase, indicating that the steric hindrance effect do not affect liquid crystalline behavior of the polymers. The dynamic light scattering results demonstrated that P(1-M-2-HEPVTA) exhibited lower cloud point compared with that of P(2-HPPVTA) at the same mass concentration and the same molecular weight. The more significant molecular weight and concentration dependence on cloud point have been observed in P(2-HPPVTA) solution than in P(1-M-2-HEPVTA) solution. We also discovered that the cloud points of both P(2-HPPVTA) and P(1-M-2-HEPVTA) solution are lower in D 2 O than in H 2 O. It is noted that the cloud point of PM-2 is 9.9 C lower in D 2 O than in H 2 O, much less pronounced than the cloud point difference of PH-2. The differences of thermo-responsive behaviors between P(2-HPPVTA) and P(1-M-2-HEPVTA) were resulted from the steric hindrance effect existed in their side groups.

Advancing the Development of Highly-Functionalizable Glucose-Based Polycarbonates by Tuning of the Glass Transition Temperature

“…Therefore, tailoring and broadening the T g range of sugarbased polycarbonate materials would further enable their usage in fields such as stretchable and self-healing materials, 18 drug delivery vehicles, 19 and soft implants/scaffolds. 20 Variation of T g has been extensively studied for traditional linear polymers and dendrimers, where T g is shown to correlate with certain parameters, including molar mass, 21,22 chemical composition of the backbone, 23 steric hindrance of substituents, 24 side chain flexibility, 25 chain-end composition, 26 intermolecular interaction between polymer chains, 27 crosslinking density, 28 and dispersity. 29 Under the guidance of polymer physics, various methods have been utilized in tailoring T g .…”

Synthesis, Mesomorphism and Photoluminescence of a New Class of Anthracene-based Discotic Liquid Crystals

“…The low intensity and broad shape of the reflections indicate poor molecular packing and hence reduced interaction. So, from the aforesaid data, it is confirmed that compound 4.4 shows columnar nematic phase (N Col ), which is uncommon in the family of discotics.…”

Bulk and solution properties of a thermo-responsive rod–coil block polymer based on poly(N-isopropylacrylamide)

“…Homo-PHIPPVTA is a type of mesogen-jacketed liquid crystal polymer (MJLCP). 44,46 In order to explore the liquid-crystalline behaviors of PNIPAm-b-PHIPPVTA, polarized light microscope (PLM) and one-dimensional wide angle X-ray diffraction (1D WAXD) were employed. The block copolymer samples were amorphous when the molecular weight is lower than a critical molecular weight of approximately 2.76 Â 10 4 g mol À1 for the N 43 bH x and 4.48 Â 10 4 g mol À1 for the N 151 bH x , respectively.…”

“…PHIPPVTA separate from aqueous solution as the temperature exceeded cloud point due to the conguration transformation from hydrophilic soluble chains to hydrophobic collapsed domains. 44,46 Incorporation of more hydrophobic (lowering the LCST) comonomers (NIPAm) into homopolymer chains with unusual thermo-responsive properties resulted in the cloud point changes. 45 Herein, the rod-coil diblock copolymers with PHIPPVTA rod units and exible PNIPAm coil were precisely controlled to clarify the inuence of chain length and polymer composition on the thermo-responsive behavior.…”

“…[43][44][45] Unusual solution phase transition trend of the semirigid water-soluble polymers were explored for the rst time by our group. [44][45][46] The molecular structure and molecular weight of this semirigid water-soluble thermo-responsive polymers based on mesogen-jacketed liquid crystal polymers easy to control. Encouraged by those results, we designed and synthesized a series of semirigid-exible block copolymers based on semi-rigid polymer (i.e., poly[bis(Nhydroxyisopropyl pyrrolidone) 2-vinylterephthalate]) and exible chain polymer (i.e., PNIPAm) via reversible addition-fragmentation chain transfer (RAFT).…”