Global Trends for kp? Expanding the Frontier of Ester Side Chain Topography in Acrylates and Methacrylates

Mechanistic aspect for the atom transfer radical polymerization of itaconimide monomers with methyl methacrylate: a computational study

Atom transfer radical polymerization (ATRP) is a versatile & famous technique for the synthesis of well defined molecular architectures. In ATRP, there is a dynamic equilibrium exists between active & dormant species. Therefore, ATRP progress through a sequence of activation & deactivation cycles, ending upon complete monomer consumption & termination reactions are minimized. This paper presents a systematic computational study on kinetics & thermodynamics associates in the ATRP of itaconimide monomers & methyl methacrylate (MMA). For this, the copolymerization system is modeled as a unimer, dimer & trimer of various itaconimides & MMA monomer. The density functional theory with B3LYP functional & 6–31 + G(d)/LanL2DZ basis sets is used in the prediction of geometries & energetics associated with the dissociation of terminal R–X bond present in the unimer, dimer & trimer. The relative equilibrium constant (K ATRP) for the ATRP activation/deactivation steps is calculated from the free energy values associated with dissociation of R–X bond. The relative K ATRP values of dimer & trimer of selected monomers is compared with their respective unimer. From the transition state geometries of the dimeric propagating radical, activation energy is calculated. The gas phase rate coefficients for propagation (k p) (of itaconimides & MMA copolymerization) are calculated using the standard transition state theory. The effect of system parameters such as solvent, temperature & substituent on K ATRP & k p values of dimer is investigated systematically. The change in the initiating system & temperature has significant effect on k p values as compared to solvent & various substituent. The K ATRP values of dimer & trimer dormant species are higher as compared to their respective monomeric species. The neighboring monomer & penultimate monomer plays vital role in kinetics & thermodynamics associated with copolymerization. The obtained initial results show that the mechanism of copolymerization of itaconimide monomers & MMA follows penultimate model.

Free-Radical Propagation Rate Coefficients of Diethyl Itaconate and Di-n-Propyl Itaconate Obtained via PLP–SEC

The propagation step is one of the key reactions in radical polymerization and knowledge about its kinetics is often vital for understanding and designing polymerization processes leading to new materials or optimizing technical processes. Arrhenius expressions for the propagation step in free-radical polymerization of diethyl itaconate (DEI) as well as di-n-propyl itaconate (DnPI) in bulk, for which propagation kinetics was yet unexplored, were thus determined via pulsed-laser polymerization in conjunction with size-exclusion chromatography (PLP-SEC) experiments in the temperature range of 20 to 70 °C. For DEI, the experimental data was complemented by quantum chemical calculation. The obtained Arrhenius parameters are A = 1.1 L·mol–1·s–1 and Ea = 17.5 kJ·mol−1 for DEI and A = 1.0 L·mol–1·s–1 and Ea = 17.5 kJ·mol−1 for DnPI.

Effect of side-group structure and temperature on chain transfer to polymer and branching in acrylate homopolymerizations

The paper reports studies of the effects of ester side-group size and structure on chain transfer to polymer (CTP) and mol% branches (%br) in the final polymers from monomer-starved semi-batch emulsion homopolymerizations of a series of alkyl acrylates with different numbers of ester OR side-group carbon atoms (NsgC) in the range 1–10. Although the high instantaneous conversions and high gel contents in the final polymers show that intermolecular CTP is significant, the kinetics have been analysed principally in terms of intramolecular CTP (intraCTP) because this is expected to be numerically the dominant CTP process. For linear OR side groups, there is a small, continuous increase in %br (from ~ 3.4 to ~ 5.0 mol%) as NsgC increases from 1 to 8, which arises predominantly from the acrylate molar mass (Macrylate) reducing the molar monomer concentration and from the small increase in rate coefficient for propagation (kp) as NsgC increases; no discernible effects of NsgC on the rate coefficient for intraCTP ($${k}_{\mathrm{trP}}^{\mathrm{intra}}$$ k trP intra ) are evident. For isomeric butyl acrylates, there is no measurable effect of isomer structure on %br (4.3–4.4 mol%), indicating that butyl groups are too small for changes in side-group bulkiness to influence $${k}_{\mathrm{trP}}^{\mathrm{intra}}$$ k trP intra and kp. A similar observation was made for n-hexyl acrylate (nHA) and 2-ethylbutyl acrylate (%br 4.7–4.8 mol%). However, cyclohexyl acrylate (cHA) gives a much higher %br (~ 7.2 mol%), which has been assigned to steric effects increasing $${k}_{\mathrm{trP}}^{\mathrm{intra}}$$ k trP intra because kp values for nHA and cHA are very similar. For OR side-groups with NsgC of 8 and10, there is a strong effect of side-group non-linearity (2-ethylhexyl, iso-octyl and iso-decyl) increasing %br, with polymers from n-alkyl acrylates having much lower %br (~ 4.5–5.0 mol%) than those from the equivalent non-linear acrylates (~ 6.7–7.1 mol%); since the kp values are expected to be similar for these acrylates, it is evident that the much bulkier non-linear OR groups cause a significant increase in $${k}_{\mathrm{trP}}^{\mathrm{intra}}$$ k trP intra compared to the linear equivalents. Tentative hypotheses for these steric effects have been postulated. Studies of the effect of temperature (0–80 °C) on CTP and %br for methyl acrylate solution homopolymerization (in which intraCTP should be completely dominant) show the expected reduction in %br as temperature reduces, such that CTP is negligible at 0 °C; Arrhenius analysis gives an activation energy of 40.7 kJ mol−1 for intraCTP, which is within the range of values reported for n-butyl acrylate.

Pulsed Laser Polymerization – Size Exclusion Chromatography Investigations into Backbiting in Ethylhexyl Acrylate Polymerization

Free radical acrylate polymerization is associated with a considerable number of side reactions occurring during chain growth. Most notably, the secondary chain propagating radicals can undergo intramolecular transfer reactions, forming...

A machine-readable online database for rate coefficients in radical polymerization

An online database created and curated by an IUPAC subcommittee is introduced.

Exploitation of the Nanoreactor Concept for Efficient Synthesis of Multiblock Copolymers via MacroRAFT-Mediated Emulsion Polymerization

Multiblock copolymers are a class of polymeric materials with a range of potential applications. We report here a strategy for the synthesis of multiblock copolymers based on methacrylates. Reversible addition-fragmentation chain transfer (RAFT) polymerization is implemented as an emulsion polymerization to generate seed particles as nanoreactors, which can subsequently be employed in sequential RAFT emulsion polymerizations. The segregation effect allowed the synthesis of a high molar mass (>100,000 g·mol^-1) decablock homopolymer at a high polymerization rate to an extent not previously achieved. A heptablock copolymer containing seven different 100 unit blocks was also successfully prepared, demonstrating how the strategy can be employed to precisely control the polymer composition at a level hitherto not accessible in environmentally friendly aqueous emulsion polymerization. Importantly, the methodology is a batch process without any intermediate purification steps, thus, rendering industrial scale up more feasible.

Polylactic acid macromonomer radical propagation kinetics and degradation behaviour

Polylactic acid (PLA) macromonomer radical homopropagation rate coefficients are evaluated as a function of average macromonomer chain length. Hydrolysis studies of nanoparticles (NP) produced from PLA macromonomers demonstrate the importance of end-group functionality on NP degradation time.

An alternative method to estimate the bulk backbiting rate coefficient in acrylate radical polymerization

An alternative method to estimate the backbiting rate coefficient in acrylate polymerization is presented and successfully applied to experimental data.

A complete kinetic study of a versatile functional monomer: acetoacetoxyethyl methacrylate (AAEMA)

The current study reports the complete kinetic analysis of acetoacetoxyethyl methacrylate (AAEMA).

Investigating the propagation kinetics of a novel class of nitrogen-containing methacrylates via PLP-SEC

The Mark–Houwink–Kuhn–Sakurada parameters as well as Arrhenius parameters of the propagation rate coefficient for a new group of nitrogen-containing methacrylates were determined via triple detector SEC and pulsed laser polymerization–size exclusion chromatography, respectively.

Synthesis, characterization, and computational study of potential itaconimide-based initiators for atom transfer radical polymerization

We report synthesis of potential initiators1a-Br,2a-Br, and3a-Br for the ATRP ofN-phenylitaconimide and MMA. We find (i) good agreement between experimentally determined and calculatedK_ATRPvalues (ii)3a-Br performs better than the commercially available initiator.