Polymeric systems bearing side‐chain 2,6‐dimethylbenzoyldiphenylphosphinoxide moieties for UV curable coatings: Synthesis and photoinitiation activity

Abstract

SYNOPSISPolymeric photoinitiators with pendant 2,6-dimethylbenzoyldiphenylphosphinoxide moieties were prepared by reacting the homopolymer of 4-acryloyloxy-2,6-dimethyl benzoic acid, and its copolymers with n-butyl acrylate with thionyl chloride followed by methoxydiphenylphosphine. These polymeric systems were characterized and their photoinitiation activity checked in the UV curing of a standard acrylic mixture, by irradiation both a t 330 and over 380 nm, the latter conditions being applied to simulate a Ti0,-pigmented coating formulation. The results were compared with those obtained by using the low molecular weight analog 2,4,6-trimethylbenzoyldiphenylphosphinoxide and previously prepared polymeric systems based on the benzoyldiphenylphosphinoxide moiety. The stability to light and to hydrolytic conditions of the polymeric photoinitiators with respect to the model compound was also tested. The results obtained are discussed and related to the structural requirements of these systems. 0 1995 John Wiley & Sons, Inc.

UV-curing of acrylic formulations by means of polymeric photoinitiators with the active 2,6-dimethylbenzoylphosphine oxide moieties pendant from a tetramethylene side chain

“…Replacement of the acyl chloride by the acylphosphine oxide (APO) absorption at 1 670 cm −1 in the second step was however incomplete. This is in agreement with previously reported results on similar acrylic polymers bearing the benzoylphosphine oxide (BPO) moieties directly attached to the backbone,20 where about 80% chloride conversion could be achieved. In addition, the presence of phosphorylated side products could also be detected in the FT‐IR, 1 H and 31 P NMR spectra of the purified polymers.…”

“…The UV‐vis spectra of the phosphorylated polymers present a tail of absorption extending beyond 400 nm due to the n → π * CO transition of APO (Figure 1 and 2). The same absorption shows a maximum at λ = 379 nm both in the low molecular weight model PI diphenyl‐(2,4,6‐trimethylbenzoyl)‐phosphine oxide (TMBPO) and in the polymeric analogues containing the 4‐acryloyloxy‐2,6‐dimethylbenzoyldiphenylphinosphoxide (ADBPO) unit 20. These latter differ from the ABDBPO polymers essentially for the presence of a p ‐methyl (TMBPO) or p ‐carbalkoxy (ADBPO) instead of a p ‐alkoxy substituent in the benzoic ring; accordingly, their molar absorptivity are quite similar, as reported in Table 2.…”

“…The flexible oligomethylene spacer improves the solubility of the polymeric PI in the acrylic polymerisation mixture, which allowed the experiments with both homo‐ and copolymer at 0.5 mol‐% BPO concentration to be carried out, in contrast to most polymeric APO PIs which could only be studied at 0.1 mol‐% photoreactive moiety 20…”

A review of the development of radical photopolymerization initiators used for designing light-curing dental adhesives and resin composites

“…On photoinitiation activity, poly(VBPO-co-MMA)s exhibited markedly improved activity than analogous aliphatic polymeric systems bearing the acylphosphine oxide moiety in the side chain 54) . On stability to daylight, poly(ADBPO-co-BA) exhibited appreciably higher stability than TMDPO, which is reported to be the most stable commercial member of this class of photoinitiators 55) .…”

“…Fig. 21 Structural formula of a polymeric photoinitiator with pendant 2,6-dimethylbenzoyl-diphenylphosphine oxide moieties 55) . Full names of poly(ADBA) and poly(ADBA-co-BA) are given in Table 1.…”