Kinetics of UV‐initiated RAFT crosslinking polymerization of dimethacrylates

Abstract

The UV-initiated RAFT polymerizations of a series of poly(ethylene glycol) dimethacrylates (PEGDMA) were investigated using differential scanning photocalorimetry (DPC) at room temperature. The rate of the RAFT system was much lower than that of a conventional free radical polymerization. A mild autoacceleration occurred as the addition reaction became diffusion controlled. The influence of the spacer length (CH 2 CH 2 O) x between the vinyl moieties of the dimethacrylates on the polymerization kinetics was examined. The polymerization rate of PEGDMA decreased with an increased x value from 4 to 9, but it increased with a further increased x value from 9 to 14. Mechanical properties of the resulting polymers were also examined by dynamic mechanical analysis (DMA). It was concluded that the presence of the RAFT agent during polymerization of multifunctional monomers did not have an effect on the heterogeneity of the polymer network. In comparison with three different PEGDMAs, the PEGDMA with the longest spacer formed the most homogeneous networks with a lower crosslinking density.

The Influence of RAFT on the Microstructure and the Mechanical Properties of Photopolymerized Poly(butyl acrylate) Networks

“…The distance to the pans was identical to the distance of the polymerizations for the tensile testing specimens. The monomer conversion and the polymerization rate were calculated as described in literature …”

“…The monomer conversion and the polymerization rate were calculated as described in literature. [ 20,22 ]…”

“…We ourselves found that thin hydrogel films of the thermoresponsive polymer poly( N ‐isopropylacrylamide) (pNIPAm), prepared by electrochemically triggered RAFT polymerization, show a strongly enhanced homogeneity of the hydrogel surfaces as studied by AFM . Photocrosslinking, however, appears to be of higher industrial importance and in the field of UV‐initiated crosslinking RAFT polymerizations, systems with multifunctional methacrylates were studied by Zhuo et al, who found that the RAFT process has a considerable influence on the curing kinetics. Leung and Bowman reported that the addition of a RAFT agent can reduce shrinkage stress of the networks .…”

Investigation on the homogeneity of PMMA gels synthesized via RAFT polymerization

“…The situation in a bulk polymerization may be different, although we do not see any indication that raising the concentration (within the limited range studied in this work) causes a noticeable change. Indeed, Ran et al argued from dynamic mechanical analysis, that using a RAFT agent did not influence the homogeneity of networks when polymerizing multifunctional monomers in bulk [18].…”

The influence of vinyl activating groups on β-allyl sulfone-based chain transfer agents for tough methacrylate networks

“…The first case, reversible AFCT (commonly shortened to RAFT) is a form of living polymerization and provides polymers with polydispersity index (PDI) values approaching unity . More recently, photo‐RAFT has been developed, however high conversions can take hours or days instead of seconds as is the usual case with (meth)acrylate polymerization . Irreversible AFCT can also be used to regulate molecular weight.…”