Modern Polymer Spect..

3.19 A Worked E.vnn~yle 193
Figure 3-57. Temperature dependence of the infrared
spectrum of n-nonadecane-1 OD: through orthorhonibic
+ c( phase transitions. Notice that (i) the orthorhombic
crystal disappears at 22.4 "C, (ii) in the c( phase at the center
of the lamella no confomiational kinks are formed
while they certainly appear in the melt (33.2"C) Combination
of the data of this figure and of Figure 3-56 are direct
evidence of 'surface melting'.
arranged in a crystal with a setting angle of 42" at T, the lattice expands anisotropically,
interlamellar forces weaken and a conformational disordering takes
place at the surface of the lamella. Such disordering is generated by the conformational
deformation of approximately 25% of the chains which tilt their head with
gauche conformation either in position 2-3 or 3-4. The inside of the lamella is not
perturbed and all chains are still trans-planar (Figure 3-58).
The next question which remains to be answered is whether surface disordering is
generated by the longitudinal motion of the chains. The following experiment has
been made [155].