Synthesis of Methacrylate-Ended Poly(n-hexyl isocyanate) Rodlike Macromonomers and Their Radical Copolymerization Behavior

Abstract

Methacrylate-ended rodlike macromonomers consisting of poly(n-hexyl isocyanate) (MA-HIC-n(2), where n is a degree of polymerization of n-hexyl isocyanate (HIC)) with narrow molecular weight distribution have successfully been synthesized in CH2Cl2 at room temperature by living coordination polymerization of HIC using 2-methacrylate ethyloxydichloro(cyclopentadienyl)titanium (IV) (1) as an initiator. The rodlike macromonomers prepared have carefully been characterized by size exclusion chromatography fitted with a multiangle laser light scattering (SEC−MALS) and 1H NMR spectroscopy. The radical copolymerization behavior of the rodlike macromonomers (M2) with methyl methacrylate (MMA) (M1) or styrene (ST) (M1) in benzene at 60 °C has thoroughly been studied and rationalized with a function of degree of polymerization of HIC. In region of degree of polymerization (n) higher than 26, the macromonomer's apparent reactivity (1/r 1) relative to MMA was found to be almost independent of n and macromonomer concentration but lower than MMA (1/r 1 is ca. 0.6). On the other hand, in the macromonomers with n less than 26, the reactivity appeared to steeply increase with decreasing n, because of weak aggregation due to hydrogen bond formation between terminal amide groups in benzene. In the copolymerization with ST (M1), the apparent reactivities (1/r 1) were also lower the reference value reported in the copolymerization of MMA with ST. The copolymerization behavior of MA-HIC-n macromonomers was compared with that of styryl-ended (VB-HIC-n, 1/r 1 ≈ 1.0) and methacryloyl-ended (Bz-HIC-n-MA, 1/r 1 ≈ 0.1) macromonomers and discussed from the structural point of views. The methacrylate functional group was thought to be much more subject to steric hindrance effects than the styrenic group.

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

“…The product was dissolved again in dry benzene, and freeze-dried under reduced pressure. 2-Methacryloyloxyethoxydichloro(cyclopentadienyl)titanium-(IV) HEMACpTiCl 2 (2) was prepared according to the reported procedures, 6 except for the use of a flask equipped with a tube containing dry triethylamine to trap HCl gas.…”

“…5,6 In brief, the initiator and dichloromethane were added to a 20 mL flask fitted with a magnetic stirrer bar. After the initiator was completely dissolved, a desired amount of HIC was added and the flask was sealed off and taken out of the drybox.…”

“…The yield is 87-90%, for use as an initiator in the polymerization of HIC. 6 Preparation of Bz-HIC-n-Ac by Termination with Acetic Anhydride (AAn) Table I shows the time-evolution of the recovered polymer yield and end-functionality of Bz-HIC-n-Ac during termination using acetic anhydride as a terminator and AlMe 3 as a Lewis acid at room temperature. At the reaction time = 0, when the PHIC living chain was directly terminated with methanol, !-Hterminated PHIC (Bz-HIC-43-H) with a relatively narrow molecular weight distribution of M w =M n ¼ 1:1 9 was prepared at relatively high conversion (87%) (run 1-1).…”

“…4 We have recently reported the preparation of 4-vinylbenzyloxy-and 2-methacryloyloxyethoxy-ended rodlike PHIC macromonomers and their fundamental radical copolymerization behavior. 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.…”

“…We have actually used this method to prepare the PHIC macromonomers described in previous papers. 5,6 However, the polymerization has to be carried out at a very high monomer concentration, usually without solvents, to obtain a high conversion to the polymer at room temperature. As a result, after the polymerization the viscosity of the reaction mixture dramatically increases and in some cases the reaction mixture solidifies.…”