Influence of chemical structure on the optical properties of new side-chain polymers containing cholesterol

Abstract

Poly[1-(cholesteryloxyhexyloxy)ethylene] (PHET) and poly [1-(cholesteryloxycarbonyl-hexyloxy)ethylene] (PHES) were prepared by reacting poly(vinyl alcohol) with cholesteryloxyhexyloxy bromides (CHB) or cholesteryloxycarbonylhexyloxy bromides (CEHB), and their thermal and optical properties were investigated. PHET and PHES exhibited monotropic cholesteric phases; however, their thermal behaviours depended on the cholesteryl groups and alkylene spacers with different chemical structures. PHET did not display reflection colours over its entire cholesteric range, whereas PHES did display reflection colours. These results suggested that the thermal stability and helical twisting power (HTP) of these polymers strongly depend on the difference in the chemical structures of the flexible spacer via cholesterol. The mesophase properties of PHET and PHES differed substantially from those of poly(cholesteryl-ω-acryloyloxyalkanoates). The results indicate that the mode of chemical linkage between the side-chain group and the main chain as well as that between the alkylene spacer and side chain play important roles in determining the thermal stability, mesophorphic structure and HTP of the cholesteric mesophases.

Steroid-Based Liquid Crystalline Polymers: Responsive and Biocompatible Materials of the Future

“…However, it does have an effect on the more flexible acrylic backbone where the LC behaviour is observed only upon passing a critical threshold of molecular weight of 12 × 10 3 gmol −1 . By switching the spacer from an ether (Figure 2A) to an equivalent ester, (Figure 2B) Yang et al demonstrated that the transition temperature to the N* mesophase shifted from −27 • C in the ether linker to 72 • C in the ester case whilst having little impact on the clearing temperature [34]. This switching of the spacer from an ether to an equivalent ester also caused the polymer to display crystallisation rather than a glass transition.…”

“…It does so by decoupling the mesogenic units and allowing them to freely form the mesophases. Both the type of the spacer and the length of the spacer are important [34]. Additionally, the stability and formation of the N* phase in polymers can be affected even by a small change in the chemical structure of the polymer.…”

Phase polymorphism and thermal stability of new cholesterol thioesters derivatives

“…Its eight chiral centres (carbon atoms) may, in principle, allow for 2 8 = 256 stereoisomers, however only one occurs in nature. Many cholesterol derivatives have cholesteric mesophases due to the presence of the cholesteryl residue in their molecular structures.…”

“…For example, imidazolium-based ionic liquid crystals bearing a cholesteryl mesogenic group were synthesised and characterised [6], effects of chain branching and lateral fluorine substitution on mesomorphism of cholesteryl benzoates has been investigated [7], as well influence of chemical structure on the optical properties of new side-chain polymers containing cholesterol was identified. [8] Cholesterol-based dimeric liquid crystals have also been studied in terms of mesomorphic properties of their frustrated phases. [9] Cholesteryl benzoate derivatives, whose transition properties were reported in [10], were also found capable of forming cholesteric liquid crystal glasses.…”

Synthesis and phase behaviour of new biodegradable liquid crystalline polycarbonate derived from side chain cholesteryl derivative

“…So far, the many LC compounds based on cholesterol or its derivatives have been reported to study optical-electric properties, thermochromism and circular dichroism. [31][32][33][34][35][36] Besides, LC materials containing cholesteryl groups have especially attracted more and more attention in the biomaterials fields. [3,[21][22][23][24][37][38][39][40][41] Stupp et al first reported the synthesis of cholesterol end functionalised oligo(L-lactic acid) and their interactions with cells.…”