Res. Chem. Intermed.
, Vol. 28, No. 1, pp. 1–11 (2002)
Infrared analysis of phase transitions in liquid crystal
acrylate monomers bearing urethanic groups
and cholesteryl as mesogen
, GHEORGHE SINGUREL
CRISTOFOR I. SIMIONESCU
, ANISOARA SOCOLIUC
and DOINA MACOCINSCHI
‘Petru Poni’ Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41 A,
‘Al.I. Cuza’ University, Bd. Carol I, 11, 6600-Iasi, Romania
Received 5 March 2001; accepted 16 September 2001
Abstract—An infrared analysis of phase transitions in three enantiotropic liquid crystalline acrylate
monomers with different spacer lengths bearing urethane groups and cholesteryl as mesogen was
carried out. Through heating and cooling, spectral modi cations especially at the level of carbonyl,
NH and urethane alkoxyl oxygen groups were found. These ndings reveal the in uence of
hydrogen bonding on mesomorphic properties of the studied compounds mentioning that both liquid
crystal transitions are evidenced by the spectral changes. For all the compounds studied, the values of
the transition temperatures deduced from the spectral modi cations are in good agreement with those
obtained from DSC measurements.
: Infrared analysis; phase transition; liquid crystal; acrylate monomer.
A number of investigations have been performed on both low molecular weight
liquid crystalline (LC) compounds and LC polymers by IR spectroscopy [1–5].
Also, the role of hydrogen bonding on LC properties of urethanic compounds is
well known [6– 13]. For example, it has been reported that for polyurethanes the
carbonyl band of the urethane group is sensitive to the state of H-bonding and
molecular aggregation [6, 7].
In , LC polyurethanes were studied by IR spectroscopy and it was found that
the carbonyl band could be resolved into three bands, i.e. the H-bonded ordered
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