(Meth)acrylic monomers with heteroatom-containing ester side chains: a systematic PLP-SEC and polymerization study

Abstract

The Arrhenius parameters of the propagation rate coefficient for two hetero-atom containing (meth)-acrylates (studied as 1 M solution in N,N-dimethylacetamide (DMAc)) are determined via the pulsed laser polymerization – size-exclusion chromatography (PLP-SEC) method. Absolute molar mass determination is achieved via SEC coupled to on-line multi-angle laser light scattering (MALLS). The data obtained for hydroxypropylcarbamate acrylate (HPCA, A = 3.97 (−1.44 to 1.63) × 10⁶ L mol⁻¹ s⁻¹ and E_a = 14.3 (−1.38 to 5.13) kJ mol⁻¹) are critically compared with the literature known data sets of two structural derivatives, i.e., 2-(phenylcarbamoyloxy)isopropyl acrylate (PhCPA) and 2-(hexylcarbamoyloxy)isopropyl acrylate (HCPA), indicating an increase in the propagation rate coefficient with increasing ester side chain length. Ureidoethyl methacrylate (UMA, A = 2.08 (−0.45 to 0.91) × 10⁶ L mol⁻¹ s⁻¹ and E_a = 19.9 (−0.89 to 0.91) kJ mol⁻¹) represents the first hetero-atom containing methacrylate to be studied via PLP-SEC, evidencing a significantly higher propagation rate coefficient compared to earlier investigated methacrylate-type monomers. Furthermore, the free-radical polymerization behavior of HPCA and UMA is studied via in situ¹H-NMR experiments at elevated temperatures allowing for an estimation of average termination rate coefficients (at low conversion) in conjunction with the determined k_p data. Furthermore, the polymerization of UMA was successfully controlled by reversible addition–fragmentation chain transfer (RAFT) polymerization as evidenced by the linear evolution of the number-average molar mass, M_n, with conversion (3000 g mol⁻¹ ≤ M_n ≤ 23 000 g mol⁻¹, 1.15 ≤ Đ ≤ 1.3) as well as by nitroxide-mediated polymerization (NMP), as demonstrated by the linear evolution of M_n with conversion (4000 g mol⁻¹ ≤ M_n ≤ 40 000 g mol⁻¹, 1.3 ≤ Đ ≤ 1.4). In addition, HPCA polymerization was successfully controlled by the RAFT process, as evidenced by the linear evolution of M_n with conversion (2000 g mol⁻¹ ≤ M_n ≤ 21 000 g mol⁻¹, 1.2 ≤ Đ ≤ 1.4) and successful chain extension experiments. Finally, the NMP of HPCA exhibited uniform shifts of the molar mass distributions in the range of 5000 g mol⁻¹ ≤ M_n ≤ 70 000 g mol⁻¹ and successful chain extension experiments.