Alkyl Block Research Articles

Crystallinity of methylene‐oxyethylene‐methylene triblock oligomers. A study of the C21, C26 and C30 di‐n‐alkyl ethers of pentadecaethylene glycol

AbstractBlock oligomers of general formula H(CH2)nO(CH2CH2O)15(CH2)nH, where n = 21, 26 and 30, were prepared. Both the oxyethylene and the alkyl blocks are homogeneous. Examination of their crystalline structure (by X‐ray scattering, Raman and IR spectroscopy and differential scanning calorimetry) reveals two characteristic forms: type II formed on slow crystallisation of oligomers with n = 21 or 26, and type III b formed on rapid crystallisation of oligomers with n = 26 or 30. Structure II has unfolded chains in a completely crystalline layer structure, with helical oxyethylene blocks and planar zig‐zag alkyl blocks. Structure III b has once‐folded chains in a partly crystalline layer structure, with non‐crystalline planar zig‐zag oxyethylene blocks and crystalline planar zig‐zag alkyl blocks.