M. Laus et al., LIQUID-CRYSTALLINE POLY(VINYL ETHER)S AND BLOCK COPOLY(VINYL ETHER)S BY LIVING CATIONIC POLYMERIZATION, Macromolecules, 29(15), 1996, pp. 5111-5118
A series of liquid crystalline (LC) poly(vinyl ether)s 1 was prepared
by living cationic polymerization of a mesogenic vinyl ether monomer,
4-butoxyphenyl 4-((6-vinylhexyl)oxy)benzoate (11), in the presence of
the HI/I-2 (1/1 mol/mol) initiating system. The number average molar m
ass of polymers 1 increased linearly with the initial monomer to initi
ator molar ratio (M(a) = 3000-15 000 g mol(-1), DPn approximate to 5-5
0), according to the living character of the polymerization, and their
molar mass distribution was rather narrow (M(w)/M(n) = 1.10-1.15). Fu
rthermore, two sets of AB diblock copoly(vinyl ether)s 2 and 3 were pr
epared by sequential polymerization of vinyl ether 11 and isobutyl vin
yl ether (12) and chiral (S)-2-methylbutyl vinyl ether (13) respective
ly, by using the same HI/I-2 system. While the average degree of polym
erization of the LC block was kept constant (DPn approximate to 10), t
he length of the non-LC block was varied (DPn approximate to 2-25), ac
cording to the chosen feed conditions. An X-ray investigation proved t
hat polymers 1 gave rise to a sequence of ordered smectic (F or I), sm
ectic C, and nematic mesophases with increasing temperature. Their tra
nsition temperatures and entropies followed slightly different molar m
ass dependences, but each of them reached a saturation value at M(n) a
pproximate to 6000 g mol(-1). The same basic mesophase polymorphism wa
s also observed for the LC block copolymers 2 and 3, thus suggesting t
hat the chemically different blocks were microphase separated within t
he solid and LC phases.