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Side‐chain liquid crystal polymers of 2,3‐disubstituted norbornenes via ring‐opening metathesis polymerization, 2 . Methoxybiphenyl as mesogenic group, influence of flexible spacer length m = 4 to 10 on the thermotropic behaviour
Author(s) -
Winkler Berthold,
Ungerank Markus,
Stelzer Franz
Publication year - 1996
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/macp.1996.021970724
Subject(s) - monomer , polymer chemistry , mesogen , polymer , polymerization , ring opening metathesis polymerisation , chemistry , glass transition , metathesis , acyclic diene metathesis , methylene , crystallography , ring opening polymerization , alkyl , materials science , organic chemistry , liquid crystalline
We report the synthesis and ring‐opening metathesis polymerization of (±)‐ exo,endo ‐bis[ω‐(4′‐methoxybiphenyl‐4‐yloxy)alkyl] bicyclo[2.2.1]‐hept‐5‐ene‐2,3‐dicarboxylates using the molybdenum‐carben initiator Mo(CH‐ t ‐Bu)(NAr)(OCCH 3 )(CF 3 )( 2 ) 2 with NAr = 2,6‐diisopropylaniline. The spacer length was varied from m = 4 to 10 methylene groups. All monomers and polymers show mesophases of the smectic type. Independently of the spacer length no glass transition was detected. An odd‐even effect of transition temperatures was observed for both the monomers and polymers. The monomers with m > 5 showed more phase transitions in the DSC‐heating runs. Dependency of liquid crystalline transition temperatures on molecular weight is shown for one polymer ( m = 6). Transition temperatures are roughly constant for polymers consisting of more than 30 repeating units. In contrast, the enthalpy changes of these transitions are nearly independent of the molecular weights once the polymers contain more than 10 repeating units, but they are strongly dependent on spacer length, with a minimum at m = 6.