Characterization of Rodlike Poly(n-hexyl isocyanate) Macromonomers and Their Polymacromonomers by Light Scattering, SAXS, Intrinsic Viscosity, and Scanning Force Microscopy

Abstract

ABSTRACT:SEC-MALS, small-angle X-ray scattering (SAXS), and viscosity measurements were made on tetrahydrofuran (THF) and n-hexane of a series of 4-vinylbenzyl and methacrylate ended poly(n-hexyl isocyanate) (PHIC) macromonomers (VB-HIC-n and MA-HIC-n, where n is a degree of polymerization of HIC and in a range from 21 to 192), together with higher molecular weight PHIC chains than the macromonomers. The molecular weight dependence of z-average mean-square radius of gyration hRg 2 i z and intrinsic viscosity [] of the macromonomers and PHIC chains in THF at 25 C were quantitatively described by the wormlike chain model with the stiffness parameter ð À1 Þ ¼ 63 nm, the molecular weight per unit contour length ðM L Þ ¼ 725 nm À1 , and the hydrodynamic diameter ðd B Þ ¼ 1:6 nm. The SAXS scattering profile of VB-HIC-57 in n-hexane at 25 C was also perfectly described in terms of the straight cylinder model. The results imply that the macromonomers may be regarded as a rigid rod molecule in THF and n-hexane. Cylindrical brushes consisting of polystyrene as a main chain and PHIC chains as a side chain were prepared by homopolymerizations of VB-HIC-46 and their dimensional properties were investigated in THF at 25 C by SAXS and SEC-MALS measurements. The molecular weight dependence of hRg 2 i z of the brushes was quantitatively explained by the wormlike cylinder model with the parameters of À1 ¼ 48 nm, M L ¼ 2:40 Â 10 4 nm À1 , the cross-sectional radius of gyration of the cylinder hRc 2 i o 1=2 ¼ 4:66 nm, and the end effect ( ¼ 16:7 nm) arising from side chains near the mainchain ends. It was concluded, therefore, that the main chain stiffness of the brush remarkably increases by the presence of densely located rodlike side chains. Direct observation of single brush of the poly(VB-HIC-46) deposited on a mica was made by scanning force microscopy (SFM) to reveal the cylindrical brushes consisting of rodlike side chains with ca. 15 nm in a thickness.

Graft Density Dependence of Main Chain Stiffness in Molecular Rod Brushes

“…24 The solid line in Figure 4 is the calculated one from eq 15 with l M = 0.22 nm, 24 perfectly describing the experimental N s dependence of ⟨S c 2 ⟩ 1/2 for the present rod brushes. Figure 5 shows the double-logarithmic plots of ⟨S c 2 ⟩ 1/2 versus the graft density (σ) of the graft copolymers, PS-g-HIC-N s -l g .…”

“…24,25,28 The value of λ M −1 of the rod brushes linearly increased with the increasing of N s that followed the scaling law of λ M −1 ∝ N s 1 . The observed power law exponent value could not be explained by the theories for the rod brushes.…”

Preparation of α-, ω-End-Functionalized Poly(n-hexyl isocyanate) Heterotelechelics

“…For the characterization of the PHIC, the elution volume in the SEC was calibrated with a series of PHICs whose molecular weight are predetermined by SEC-MALS. 7 Differential thermal analysis (DTA) of Bz-HIC-64-Ac was carried out with a TG/DTA6200 (SEIKO instrument Inc., Japan) in a nitrogen atmosphere at a heating rate of 10 C/min and was compared to that of Bz-HIC-63-H.…”

“…5,6 We have also given many details of the molecular characterizations of the rodlike macromonomers and cylindrical rod brushes found in THF at 25 C by small-angle X-ray scattering (SAXS), size exclusion chromatography-multi-angle laser light scattering (SEC-MALS), and viscometry. 7,8 When we carried out the fractionation of the cylindrical rod brushes consisting of a polystyrene main chain and PHIC side chains, however, we happened to meet a serious problem of degradation of the PHIC side chains. In general, the fractionation of PHIC chain is carried out with a solvent mixture of benzene as a good solvent, and methanol as a precipitant.…”

Synthesis of Oligo(oxyethylene) Methacrylate-ended Poly(n-hexyl isocyanate) Rodlike Macromonomers and Their Radical Copolymerization Behavior with Methyl Methacrylate

“…16 We have recently reported the syntheses of 4-vinylbenzyloxy-and 2-methacryloyloxyethoxy-terminated rodlike PHIC macromonomers (VB-HIC-n-H and MA-EO 1 -HIC-n-H, where n is the degree of polymerization of HIC), their fundamental radical copolymerization behavior and many molecular characterization details. [21][22][23][24] In the radical copolymerization of MA-EO 1 -HIC-n-H (M 2 ) with MMA (M 1 ), the apparent reactivity of the macromonomer (1/r 1 ) relative to MMA decreased down to ca. 0.6.…”