Case Study 3 Orientation in Block Copolymers - Raman Scattering

PB28-PU1 at a temperature of — 20°C. This value was determined to be 0.72 by calculating the limiting slope of the data near the origin. The dashed, straight line represents the least-squares fit of the data in the linear region near the origin. 

5 Case Study 3 Orientation in Block Copolymers - Raman Scattering 

Block copolymers consist of chemically distinct polymer chains that are tethered together to form a single macromolecule. If the individual blocks are immiscible when they are unattached, phase separation will also normally occur in the case of the copolymer, with morphologies that depend on the relative composition of the separate block species, and their manner of attachment (diblocks, triblocks, stars, etc.). This is a result of the physical connection of the blocks, which prevents them from separating over distances greater than the contour lengths of the respective blocks. The result is a microphase separation with adjacent domains that are richer in either of the chemical species. 

Recently, a theoretical description of microphase separation in block copolymer by Semonov has assumed significant chain stretching [185]. This work demonstrated that this assumption simplifies the description of the thermodynamics of block copolymers un- 

To use Raman scattering as a method of isolating the orientation of the individual blocks of the sample, Raman scattering spectra were examine to ensure that each block yielded separate, identifiable peaks. For the PS-PBD system, these are provided by the C-C aromatic-aliphatic stretching vibration of the PS at a frequency of 1029 cm-1, and at 

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