Influencing factors on liquid crystalline properties of cholesterol side-chain liquid crystalline polymers without spacer: molecular weight and copolymerisation

ABSTRACT

It is a challenge to tailor the phase behavior and phase structure of side-chain liquid crystalline polymers carrying targeted ordered structures and functional properties. In this work, liquid crystalline (LC) properties of cholesterol side-chain polymers without spacer were controlled by molecular weight (M_n) and copolymerization. On the one hand, two series of homopolymers without the spacer, poly (methacrylic acid) cholesterol esters (PCholMC_n) and poly (acrylic acid) cholesterol esters (PCholAC_n) with different M_n and low polydispersity, were achieved by reversible addition-fragmentation chain transfer polymerization. The experiment results indicated that the M_n had little effect on the LC properties of PCholMC_n and all homopolymers formed the smectic A phase. However, the phase structures of PCholAC were found to be strongly M_n dependent. The polymers PCholAC_n were amorphous when the M_n was lower than a critical value of approximately 1210₃ g/mol. But when the M_n exceeded the critical value, the polymers exhibited smectic A phase. On the other hand, two kinds of random copolymers, poly(cholest-5-en-3-methacrylate)-co-polymethyl acrylate (PCholMC-co-MA) and poly(cholest-5-en-3-acrylate)-co-polymethyl acrylate (PCholAC-co-MA) were synthesized with various composition. The findings suggested that the steric effect of main-chain and the interaction of mesogens would promote the formation of LC phase.

Graphical abstract

The phase behavior and phase structure of side-chain liquid crystalline polymers without flexible spacer: poly (acrylic (meth) acid) cholesterol esters, was tailored by the molecular weight and copolymerization.

KEYWORDS:

• Cholesterol side-chain liquid crystalline polymers
• copolymerisation
• molecular weight effect
• phase behaviour
• phase structure

Acknowledgments

This research was financially supported by the Nature Science Foundation of Hunan Provinces (2017JJ3294), the National Natural Science Foundation of China (21504075), Project supported by State Key Laboratory of Powder Metallurgy, Central South University, Changsha, China.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was financially supported by the the Nature Science Foundation of Hunan Provinces [2017JJ3294];the National Natural Science Foundation of China [21504075]. This project was supported by State Key Laboratory of Powder Metallurgy, Central South University, Changsha, China.