Ethylene Glycol Dicyclopentenyl (Meth)Acrylate Homo and Block Copolymers via Nitroxide Mediated Polymerization

Abstract

Nitroxide-mediated polymerization (NMP), (homo and block copolymerization with styrene (S) and butyl methacrylate/S) of ethylene glycol dicyclopentenyl ether (meth)acrylates (EGDEA and EGDEMA) was studied using BlocBuilder alkoxyamines. EGDEA homopolymerization was not well-controlled, independent of temperature (90-120 °C), or additional free nitroxide (0-10 mol%) used. Number average molecular weights (M_n) achieved for poly(EGDEA) were 4.0-9.5 kg mol^-1 and were accompanied by high dispersity (Ð = M_w/M_n = 1.62-2.09). Re-initiation and chain extension of the poly(EGDEA) chains with styrene (S) indicated some block copolymer formation, but a high fraction of chains were terminated irreversibly. EGDEA-stat-S statistical copolymerizations with a low mol fraction S in initial feed, f_S,0 = 0.05, were slightly better controlled compared to poly(EGDEA) homopolymerizations (Ð was reduced to 1.44 compared to 1.62 at similar conditions). EGDEMA, in contrast, was successfully polymerized using a small fraction of S (f_S,0 ~ 10 mol%) to high conversion (72%) to form well-defined EGDEMA-rich random copolymer (molar composition = F_EGDEMA = 0.87) of M_n = 14.3 kg mol^-1 and Ð = 1.38. EGDEMA-rich compositions were also polymerized with the unimolecular succinimidyl ester form of BlocBuilder initiator, NHS-BlocBuilder with similar results, although Ðs were higher ~1.6. Chain extensions resulted in monomodal shifts to higher molecular weights, indicating good chain end fidelity.

Keywords: block copolymers; copolymerization; nitroxide mediated polymerization.

Figure 1

Structures of BlocBuilder, SG1 free nitroxide and ethylene glycol dicyclopentenyl ether (meth)acrylate (EGDEA and EGDEMA).

Figure 2

¹H NMR of a sample of the reaction mixture for the homopolymerization of EGDEA (Expt. ID: E-T90, temperature = 90 °C, t_{polymerization} = 150 min, M_n = 3.0 kg mol⁻¹, Ð = 1.54).

Figure 3

¹H NMR of an EGDEMA/S copolymer (EGDEMA/S-N-80-90) with M_n = 5.6 kg mol⁻¹, Ð = 1.27, F_S = 0.77. Note that the cyclopentenyl peaks at about 5.5 ppm were used to indicate EGDEMA composition while the aromatic protons at 6.5–7.0 ppm were used to indicate S composition.

Figure 4

Semi-logarithmic kinetic plots of ln[(1−X)⁻¹], where X represents the overall monomer conversion, versus time for ethylene glycol dicyclopentenyl ether acrylate (EGDEA) homopolymerizations at 90–120 °C via nitroxide mediated polymerization with BlocBuilder^TM and 5 mol% additional SG1 free nitroxide relative to BlocBuilder^TM.

Figure 5

Number average molecular weight (M_n) and dispersity (Ð) of homopolymers of ethylene glycol dicyclopentenyl ether acrylate (EGDEA) with r = 0.05 (added free SG1 nitroxide relative to BlocBuilder initially) at various temperatures (E-T90 = EGDEA homopolymerization at 90 °C; E-T100 = EGDEA homopolymerization at 100 °C; E-T110 = EGDEA homopolymerization at 110 °C; E-T120 = EGDEA homopolymerization at 120 °C). The straight solid line indicates the predicted M_n versus conversion if the polymerization was living (M_{n, theoretical} at 100% conversion ≈ 20 kg mol⁻¹ for this set of polymerizations).

Figure 6

Semi-logarithmic kinetic plots of ln[(1−X)⁻¹], where X represents the overall monomer conversion, versus time for ethylene glycol dicyclopentenyl ether acrylate (EGDEA) homopolymerizations at 90 °C via Nitroxide-Mediated Polymerization with BlocBuilder^TM and r = 0–10% excess SG1 free nitroxide relative to BlocBuilder^TM.

Figure 7

Number average molecular weight (M_n) and dispersity (Ð) of homopolymers of ethylene glycol dicyclopentenyl ether acrylate (EGDEA) measured by GPC calibrated with poly(methyl methacrylate) standards (symbols: E-0 (r = 0): blue diamonds, E-5: red squares (r = 0.05), E-10: green triangles (r = 0.10)).

Figure 8

Number-average molecular weight (M_n) and dispersity (Ð) versus conversion of (a) EGDEA homopolymerization and (b) EGDEA/S copolymerization with f_S,0 = 0.05 in the initial monomer composition at 90 °C. This data is referred to expt. IDs EGDEA and EGDEA/S in Table 7.

Figure 9

Number-average molecular weight (M_n) and dispersity (Ð) of statistical copolymer of ethylene glycol dicyclopentenyl ether methacrylate (EGDEMA) and styrene (S) measured by GPC calibrated with poly(methyl methacrylate) standards (Expt. ID. EGDEMA/S in Table 7). This polymerization was done at 90 °C in 50 wt.% dioxane solution.

Figure 10

GPC traces of corresponding macroinitiator EGDEA (dashed line, sample E-T90, M_n = 4.0 kg mol⁻¹, Ð = 1.62) and chain extended block copolymer EGDEA-S (solid line, M_n = 58.6 kg mol⁻¹, Ð = 1.97, F_EGDEA = 0.08). Chromatogram of chain-extended block copolymer showed no significant change after fractionation.

Figure 11

GPC chromatograms of the chain extension with styrene at 100 °C from a poly(EGDEMA-stat-S) macroinitiator (see Table 8 for properties of the macroinitiator with ID = EGDEMA/S-15-90).

Figure 12

GPC traces from an EGDEMA/S macroinitiator (EGDEMA/S-N-80-90, M_n = 5.6 kg mol⁻¹, Đ = 1.27, F_EGDEMA = 0.23) to the chain extended species with BMA/S at various polymerizations to form the poly(EGDEMA/S-block-BMA/S) block copolymer (M_n = 32.3 kg mol⁻¹, Đ = 1.69, F_BMA= 0.64, F_EGDEMA = 0.05).

Figure 13

¹H NMR spectrum in CDCl₃ of poly(EGDEMA/S-block-BMA/S) showing the integrations to provide the overall compositions of the block copolymer.