Molecular-weight dependence of the formation of highly ordered lamellar structures of poly(N-dodecyl acrylamide) by humid annealing. Issue 7 (24th January 2019)

• Record Type: Journal Article
• Authors: Ebata, Kazuki; Hashimoto, Yuki; Ebara, Kohei; Tsukamoto, Mayu; Yamamoto, Shunsuke; Mitsuishi, Masaya; Nagano, Shusaku; Matsui, Jun
• Is Part Of: Polymer chemistry. Volume 10:Issue 7(2019)
• Page Start: 835
• Page End: 842
• Publication Date: 2019-01-24
• Subjects: Polymers -- Periodicals; Macromolecules -- Periodicals; Polymerization -- Periodicals; 547.705
• DOI: 10.1039/c8py01660g
• Languages: English
• ISSNs: 1759-9954

Abstract

Abstract : Highly oriented lamellar films of poly( N -dodecylacrylamide) with high molecular weights were formed by nanosegregation between alkyl side chains and a water-adsorbed main chain. Abstract : The molecular-weight dependence of the formation of highly ordered lamellar structures of poly( N -dodecylacrylamide) (pDDA) during humid annealing was studied. For this purpose, pDDA polymers with a number-average molecular weight ( M n ) ranging from 1200 to 52 000 were synthesized by free radical polymerization. Thin films of these polymers were prepared by spin-coating and their structures were examined by X-ray diffraction (XRD) and FT-IR measurements. The XRD patterns of the spin-coated films showed a broad halo at q = 2 nm −1, which was attributed to scattering from nanosegregated alkyl domains in the case of pDDA with M n ≥ 3500 and to semi-crystalline lamellar domains in the case of pDDA with M n = 1200. Subsequently, the films were annealed at 60 °C and 95% relative humidity (humid annealing), which resulted in the formation of lamellar structures for pDDA films with M n ≥ 3500, whereby the long-range ordering of the films increased with the M n of the pDDA polymers. In contrast, pDDA with M n = 1200 afforded a semi-crystalline film even after 96 h of humid annealing. The higher M n polymers showed more disordered alkyl side chains and main chains in the lamellar film. Thus, it was concluded that the segregation between the alkyl side chains and main chains, which contain water-adsorbed amide groups, should be the driving force for the observed structural changes. Our results suggest that unique self-assembled structures can be obtained by humid annealing even from amorphous homopolymers.