Synthesis and Utilization of Low Dispersity Acrylic Macromonomer as Dispersant for Nonaqueous Dispersion Polymerization

Abstract

The effect of dispersity on the stabilization performance of poly­(butyl methacrylate) (P­(BMA)) ω-unsaturated macromonomer used as a reactive dispersant in nonaqueous acrylic dispersion (NAD) polymerization is investigated for the first time. Macromonomer with low dispersity (1.3) is synthesized in a one-pot process by the addition of bis­(difluoroboryl­diphenyl­glyoximato)­cobalt­(II) (CoPheBF) as a catalytic chain transfer (CCT) agent to P­(BMA) chains mediated by atom transfer radical polymerization (ATRP); addition of the CoPheBF at a BMA monomer conversion of ∼80% leads to good control of chain length and dispersity while achieving a high fraction of terminal double bond (TDB) functionality. The lower dispersity P­(BMA) macromonomer provides better stabilization to NAD systems per dispersant chain compared to material of the same number-average molecular weight (∼6000 Da) and TDB functionalization (∼70–75%) but higher dispersity (1.8), as characterized by the smaller average particle sizes and the higher weight fractions of incorporated dispersant.

Modeling the Synthesis of Butyl Methacrylate Macromonomer by Sequential ATRP‐CCTP

“…In the experimental study, it was hypothesized that a higher proportion of the longer product chains are not macromonomers, as the soluble polymer recovered after dispersion polymerization contained a greater fraction of high‐MW material compared to the MMD of the original distribution. As Predici provides a representation of the full MMD, this hypothesis can be investigated by comparing the distributions of the three different types of polymer chains tracked by the simulation, macromonomer, bromine‐capped chains, and terminated saturated chains (dead chains); the latter two distributions are combined to make up the material termed herein as “polymer without vinyl end groups.”…”

“…The experimental procedures and recipe were outlined in a previous paper . The batch reaction was conducted in a stirred vessel controlled at 70 °C in 50 wt% anisole with initial molar ratios of [BMA] 0 :[EBiB] 0 :[CuBr] 0 :[PMDETA] 0 of 42:1:0.4:0.8.…”

“…The reaction recipe and conditions are the same as previously described, with the CoPheBF chain transfer agent added to the system after the ATRP reaction had proceeded for 2 h, corresponding to roughly 80% monomer conversion. The reaction was stopped at 4 h by exposure to the air and the product isolated as described above.…”

“…It was demonstrated that poly(methyl methacrylate) (P(MMA)) macromonomer with high vinyl end‐group functionality and low Ð could be synthesized through the combination of both techniques, with the CCT agent bis{μ‐[(2,3‐butanedione dioximato) (2‐) O:O′]} tetrafluorodiborato(2‐)‐ N , N ′, N ′′, N ′′′ cobalt (II) (CoBF) or 5,10,15,20‐tetraphenyl‐21H, 23H‐porphine cobalt(II) Co(tpp) ( Figure 1 ) added toward the end of polymerization to add terminal double bonds (TDB) to the uniform chains mediated by ATRP chemistry . Very recently, low D poly(butyl methacrylate) (P(BMA)) was synthesized through this sequential ATRP‐CCTP technique using bis(difluoroboryldiphenylglyoximato)cobalt(II) (CoPheBF, Figure ) as the CCT agent; the study showed that lowering the dispersity of macromonomer by this strategy improved its efficiency as a dispersant in nonaqueous dispersion polymerization compared to a similar material with a dispersity of 2 …”

“…Starting from estimates from the literature, the activation and deactivation coefficients are adjusted to provide a representation of the experimentally measured conversion, average chain length, and dispersity profiles, with the influence of the mode of termination on the production of TDBs during the ATRP reaction is also investigated. The model is then used to explore the influence of operating conditions on the extent of TDB functionalization achieved in the system, as well as to explore whether the high‐molar‐mass polymer chains in the distribution are more likely to be dead chains terminated by combination, a hypothesis put forth to explain results obtained when using the low Đ macromonomer P(BMA) as the dispersant in nonaqueous dispersion polymerization …”