Premium
Synthesis of New Side‐Chain Liquid‐Crystalline Polyoxetanes with Two Mesogenic Groups Connected by a Flexible Spacer in the Side Chain
Author(s) -
del Campo Aránzazu,
Bello Antonio,
Pérez Ernesto
Publication year - 2002
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20020401)203:7<975::aid-macp975>3.0.co;2-4
Subject(s) - mesogen , oxetane , side chain , polymer chemistry , monomer , steric effects , cationic polymerization , polymer , oligomer , differential scanning calorimetry , chemistry , polymerization , ether , crystallography , materials science , stereochemistry , organic chemistry , liquid crystalline , physics , thermodynamics
The synthesis of a different geometry of side‐chain liquid‐crystalline polymers is reported where two mesogenic units connected by a flexible spacer are attached as pendent groups of a polymeric chain. The resulting structure is the following, where R 1 , R 2 and R 3 are methylenic or oxymethylenic segments: The monomers were obtained by linking the dimer structure to an oxetane ring. These substituted oxetanes were polymerised by a boron trifluoride‐initiated cationic ring‐opening reaction to obtain the corresponding polymers. The polymerisation proceeds with high yields, in spite of the steric hindrance derived from the bulkiness of the side chain, and the presence of some functional groups in the molecule that compete against the cyclic ether for the nucleophilic attack at the propagating centre. A fraction of cyclic oligomer is obtained together with high molecular‐weight polyoxetane, as a result of back‐biting reactions during the polymerisation. Several systems with spacers of different length and parity were synthesised in order to analyse the influence of the nature of the spacer on the phase behaviour. The formation of mesophases was proved by means of differential scanning calorimetry, X‐ray diffraction and microscopic analysis. Most of the monomers form smectic structures at subambient temperatures. The polymers display a similar phase behaviour, although shifted to higher temperatures.