A novel photoinimer for the polymerization of acrylates and methacrylates

Abstract

A new class of multifunctional photoinitiating system based on 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM), N,N,N 0 -trimethylethylenediamine (TMED) and 3-benzoylbenzoyl chloride present in the same molecule has been synthesized and characterized by 1 H and 13 C NMR spectroscopy. This self-contained photoinitiator-monomer (photoinimer) was used to efficiently initiate polymerization of acrylates and methacrylates. Both rate of polymerization and percentage conversion increased with increase in initiator concentration. An increment in rate of polymerization observed when the benzophenone moiety was directly attached to the parent molecule (obtained from the Michael addition reaction between AHM and TMED) appears to be due to proximity effect: chemical bonding provides a high local concentration of both components of the photo-activated system involving benzophenone and a hydrogen atom source from an electron-rich tertiary amine. For the three initiating systems investigated, lowering the initiator concentration plays an important role; i.e., the polymerization rate for the chemically linked system was about two times faster than the mixed initiating system.

Photopolymerization kinetics of 2-phenylethyl (meth)acrylates studied by photo DSC

“…1) are of expected nature as reported in literature [2,10,27]. The initial ascending nature of the rate curve is due to initiation followed by autoacceleration and diffusion controlled polymerization processes while the later descending nature of the rate curve is the deceleration step where an increase in viscosity during photopolymerization can impart restriction to the mobility of polymerizing moieties.…”

“…However an increase in temperature resulted in a decrease in R p max . This behavior of formulations involving acrylate is due to high initial rate of polymerization than methacrylate [27]. With increase in temperature even though the radical mobility is enhanced, a faster autoacceleration will result in instantaneous viscosity build up which occur before R p max at higher temperature.…”

Structure-reactivity relationships of novel monomeric photoinitiators

“…Small molecular weight commercial photoinitiators do not exhibit all of these properties. Therefore, in recent years, the development of monomeric (MPI) [5][6][7][8][9][10][11][12] and polymeric photoinitiators (PPIs) [13][14][15][16][17][18][19][20][21][22][23][24][25] which do, has become an important issue.…”

Synthesis and photopolymerization kinetics of a photoinitiator containing in-chain benzophenone and amine structure

“…Most of type II photoinitiators are based on benzophenone (BP) [11], and their photoefficiency can be promoted in the presence of hydrogen donors such as tertiary amine [12]. Structures based on BP chromophore have attracted intensive academic and industrial interest.…”