Macromolecular Crystal Engineering Based on Segmented Polymers: Influence of Heteroatoms on the Thermal Properties and Crystallization of m,n‐Polyurethanes Derived from Long‐Chain, Heteroatom‐Containing, Monodisperse α,ω‐Diols

Abstract

Long‐chain heteroatom‐containing telechelic diols with 29–32 atoms in the backbone were synthesized by a one‐step, free‐radical telomerization of 10‐undecene‐1‐ol with commercially available α,ω‐dithiols. The oxygen and sulfur atoms caused a decrease in the melting point and enthalpy of the diols, compared to the corresponding purely aliphatic diols. The heteroatom‐containing α,ω‐diols HO(CH2)11S(CH2)2X(CH2)2S(CH2)11OH, where X = CH2, O, or O(CH2)2O, were reacted in the melt with 1,6‐diisocyanatohexane OCN(CH2)6NCO, producing a series of polyurethanes containing an increasing amount of heteroatoms. Characterization by differential scanning calorimetry, infra‐red spectroscopy, thermogravimetric analysis, and wide angle x‐ray scattering of the m,n‐polyurethane series showed that, like the telechelic diols they were synthesized from, the heteroatoms caused a decrease in the melting point and enthalpy. However, they did not affect either the decomposition temperature or the crystal structure/packing.Typical decomposition behavior of all the heteroatom‐containing m,6‐polyurethane.magnified imageTypical decomposition behavior of all the heteroatom‐containing m,6‐polyurethane.

Structure of 22,12-Polyurethane in Chain-Folded Lamellar Crystals

“…where m ) 12, 22, or 32 and n ) 4, 6, 8, or 12. [1][2][3][4] These syncephlic 5 chain molecules were synthesized by step polyaddition of the appropriate aliphatic diol and diisocyanate. In general, it was found that this polyurethane family crystallized from both the melt and solution in the form of thin (≈10-18 nm) lamellae and the estimated chain length was an order of magnitude greater than the measured lamellar thicknesses, and therefore, chain-folding is expected in these lamellar crystals.…”

Bio-Based Aromatic Copolyesters: Influence of Chemical Microstructures on Thermal and Crystalline Properties

“…Functional groups on the main chains or side chains are critical for thermal stability. For example, heteroatoms (N, O, S) can easily degraded under high temperature or in the presence of oxygen [19][20][21][22]. Ester, urethane or carbonate groups are also easily attacked by other chemicals in the reaction systems, and thus, cause the scission of polymer chains [23][24][25][26].…”