Exploiting Addition–Fragmentation Reactions to Produce Low Dispersity Poly(isobornyl acrylate) and Blocky Copolymers by Semibatch Radical Polymerization

Abstract

Solution radical homopolymerization of isobornyl acrylate (iBoA) under starved‐feed higher temperature conditions unexpectedly leads to polymer product with low dispersity (<1.3) compared to the polymerization of butyl acrylate (BA) under identical conditions. Both backbiting and β‐scission reactions occur, as the poly(iBoA) product contains close to 100% terminal double bond (TDB) functionality. However, the addition of monomer to the midchain radicals formed by backbiting is sterically hindered, greatly reducing both short and long‐chain branching. The poly(iBoA) macromonomer functions as an excellent addition–fragmentation agent, not only lowering dispersity but also providing a means to efficiently produce blocky acrylate copolymers through sequential monomer feeding in the starved‐feed semibatch process.

Measurement and Modeling of N‐tert‐butyl Acrylamide Radical Homo‐ and Copolymerization with Methyl Acrylate in Ethanol/Water

“…[ 32 ] t‐BuAAm backbiting is expected since the SP‐PLP‐EPR study by Kattner and Buback conclusively showed that MCR radicals form in the AAm system, [ 26 ] and since the mechanism has been shown to occur with all acrylate monomers irrespective of the ester group structure. [ 28,45 ] The reduced rate of monomer conversion that occurs as w mon , 0 is decreased from 0.20 and 0.10 (Figure 1a) provides strong evidence of t‐BuAAm backbiting, and omitting the reaction from the model resulted in systematic overprediction of the experimental batch conversion profiles under conditions for which the influence of backbiting is increased (i.e., at higher temperature and reduced w mon , 0 ). Thus, the $$k_{{\rm{bb}}}^{{\rm{t - BuAAm}}}$$ values were fitted to batch conversion profiles at 60 °C and 70 °C, while assuming that the activation energy for the reaction is the same as reported for AAm.…”

Tacticity control approached by electric-field assisted free radical polymerization – the case of sterically hindered monomers

“…, backbiting), (ii) βC-scission reactions and (iii) intermolecular chain transfer. 29–31 Notably, backbiting and βC-scission side reactions can slow down the polymerization process, shortening the length of the main chain and producing macromonomers. However, the electron paramagnetic resonance (EPR) measurements have revealed that these reactions are expected to become important at elevated temperatures.…”

“…On the other hand, one should bear in mind that FRP of IBA similar to other acrylate monomers, might often be accompanied by the occurrence of unwanted side reactions such as (i) intramolecular chain transfer (i.e., backbiting), (ii) βC-scission reactions and (iii) intermolecular chain transfer. [29][30][31] Notably, backbiting and βC-scission side reactions can slow down the polymerization process, shortening the length of the main chain and producing macromonomers. However, the electron paramagnetic resonance (EPR) measurements have revealed that these reactions are expected to become important at elevated temperatures.…”

The Use of High‐Temperature Semi‐Batch Radical Polymerization to Synthesize Acrylate Based Macromonomers and Structured Copolymers

“…The U% was combined with the DP n determined by SEC analysis to estimate the percentage of chains that contain a TDB. [12] 13 C NMR was conducted using a 500 MHz Bruker Avance NEO spectrometer at room temperature. The samples were prepared by dissolving the dried polymer in CDCl 3 to ≈20 wt.% polymer.…”