ORDER-DISORDER TRANSITION IN COMB-LIKE BLOCK-COPOLYMERS OBTAINED BY HYDROGEN-BONDING BETWEEN HOMOPOLYMERS AND END-FUNCTIONALIZED OLIGOMERS - POLY(4-VINYLPYRIDINE)-PENTADECYLPHENOL
J. Ruokolainen et al., ORDER-DISORDER TRANSITION IN COMB-LIKE BLOCK-COPOLYMERS OBTAINED BY HYDROGEN-BONDING BETWEEN HOMOPOLYMERS AND END-FUNCTIONALIZED OLIGOMERS - POLY(4-VINYLPYRIDINE)-PENTADECYLPHENOL, Macromolecules, 30(7), 1997, pp. 2002-2007
Dynamic mechanical spectroscopy (DMS) is used to further investigate t
he recently observed order-disorder transition (ODT) in comblike block
copolymers obtained by hydrogen bonding between poly(4-vinylpyridine)
and pentadecylphenol (P4VP-PDPx). For stoichiometric amounts of pyrid
ine and phenol, i.e., z = 1.0, the ODT to a lamellar structure occurs
at T similar or equal to 65 degrees C. The dynamic moduli G' and G ''
simultaneously show a crossover from a liquidlike behavior (G' similar
to omega(1.5) and G '' similar to omega) to a response intermediate b
etween a Newtonian fluid and a solid (G' approximate to G'' similar to
omega(1/2)). The behavior above T-ODT differs slightly from a homopol
ymer melt (G' similar to omega(2.0)) due to composition fluctuations,
whereas the behavior below T-ODT is characteristic for quenched block
copolymer lamellar phases with local uniaxial order and global isotrop
y. Near room temperature, a transition to solid behavior (G similar to
omega(0)) takes place due to crystallization of the alkyl side chains
. Larger amounts of PDP lower the T-ODT temperature, and for x = 2.0 t
he transition to solid response occurs directly from the disordered st
ate. Small and wide angle X-ray scattering (SAXS and WAXS) experiments
and differential scanning calorimetry (DSC) corroborate these finding
s. Furthermore, SAXS and WAXS demonstrate that the low-temperature sta
te of P4VP-PDP2.0 is not stable and indicate that ultimately macrophas
e separation into a pure crystalline PDP phase and a microphase separa
ted P4VP-PDP phase occurs.