Acrylates, photopolymerization

Polymerization Rate Dependence on Residual Polymerization Heat Lauryl Acrylate Photopolymerization... 

A calorimetric study of acrylate photopolymerization. J. Polym. Sci. Polym. Phys. Ed., 17, 2059-2075. 

Cramer, N. B. and Bowman, C. N. 2001. Kinetics ofthiol-ene and thiol-acrylate photopolymerizations with real-time fourier transform infrared. /Polym Set Part A-Polym Chem 39 3311-19. 

The features and detail of the IPN kinetics were also studied in other works [274-276]. The kinetics of thermally initiated cationic epoxy polymerization and free radical acrylate photopolymerization were investigated in [277]. It was found that the preexistence of one polymer has a significant effect on the polymerization of the second monomer. The reaction kinetics and phase separations were studied for sequential IPNs in [278]. The kinetics of IPN formation was studied for IPNs based on PDMS-cellulose acetate butyrate [279]. All these and other works [280-282] confirm the general regularities of the reaction kinetics and its connection with phase separation in forming systems. 

The well-known photopolymerization of acrylic monomers usually involves a charge transfer system with carbonyl compound as an acceptor and aliphatic tertiary amine, triethylamine (TEA), as a donor. Instead of tertiary amine such as TEA or DMT, Li et al. [89] investigated the photopolymerization of AN in the presence of benzophenone (BP) and aniline (A) or N-methylaniline (NMA) and found that the BP-A or BP-NMA system will give a higher rate of polymerization than that of the well-known system BP-TEA. Still, we know that secondary aromatic amine would be deprotonated of the H-atom mostly on the N-atom so we proposed the mechanism as follows ... 

Polymers in Schemes 12 and 13 were the first examples of the preparation of pyridinium and iminopyridinium ylide polymers. One of the more recent contributions of Kondo and his colleagues [16] deals with the sensitization effect of l-ethoxycarbonyliminopyridinium ylide (IPYY) (Scheme 14) on the photopolymerization of vinyl monomers. Only acrylic monomers such as MMA and methyl acrylate (MA) were photoinitiated by IPYY, while vinylacetate (VA), acrylonitrile (AN), and styrene were unaffected by the initiator used. A free radical mechanism was confirmed by a kinetic study. The complex of IPYY and MMA was defined as an exciplex that served as a precursor of the initiating radical. This ylide is unique in being stabilized by the participation of a... 

The second section focuses on emerging classes of photopolymerizations that are being developed as alternatives to acrylates. Three types of polymerization systems are included cationic photopolymerizations, initiator-free charge-transfer polymerizations, and a thiol-ene reaction system. The last section covers four interesting emerging applications of photopolymerization technology. 

The objective of the present work was to determine the influence of the light intensity on the polymerization kinetics and on the temperature profile of acrylate and vinyl ether monomers exposed to UV radiation as thin films, as well as the effect of the sample initial temperature on the polymerization rate and final degree of cure. For this purpose, a new method has been developed, based on real-time infrared (RTIR) spectroscopy 14, which permits to monitor in-situ the temperature of thin films undergoing high-speed photopolymerization, without introducing any additive in the UV-curable formulation 15. This technique proved particularly well suited to addressing the issue of thermal runaway which was recently considered to occur in laser-induced polymerization of divinyl ethers 13>16. 

Fig.3 Influence of the light intensity on the photopolymerization of a polyurethane-acrylate (PUA) film. — IR response time...

Table 1 Influence of the temperature on the photopolymerization of a polyurethane-acrylate resin (Light intensity 11 mW cm 2) ...

The chapters in this book are organized into three sections. A majority of the commercial photopolymerization systems are based on acrylate monomers therefore, the first several chapters focus on fundamental characterization of... 

General Electric Co.) were added to the acrylic and epoxy monomers, respectively, to initiate photopolymerization. The acrylic monomers that polymerized by a free-radical mechanism were irradiated under nitrogen. The output of the lamp measured at the substrate was about 4 mW/cm2 at 260 nm and about 11 mW/cm2 at 310 nm. 

Conventionally, solutions of acrylamide or other acrylic monomers, or mixtures of them, can be photopolymerized onto flat glass surfaces which have previously been derivatized with acrylic groups to promote covalent and robust binding of the gel (e.g. by reaction with 3-(triethoxysilylpropyl)acryla-mide) [59]. Irradiation of the substrate occurs through a mask, so that poly-... 

To study the effects of composition on the photopolymerization behavior of acrylates, the group of Bowman et al. prepared gradient libraries where acrylate composition was varied in one dimension and light exposure was varied using a moveable shutter in the orthogonal direction [17-21]. An FTIR microscope was used to characterize the conversion across the samples and the data from multiple libraries was then used to derive kinetic models for the photopolymerization. 

Johnson PM, Stansbury JW, Bowman CN (2008) High-throughput kinetic analysis of acrylate and thiol-ene photopolymerization using temperature and exposure time gradients. J Polym Sci Part A Polym Chem 46 1502-1509... 

The general approach of graded radiation exposure can also be used to examine light driven processes such as photopolymerization [19]. For example, Lin-Gibson and coworkers used this library technique to examine structure-property relationships in photopolymerized dimethacrylate networks [38] and to screen the mechanical and biocompatibility performance of photopolymerized dental resins [39]. In another set of recent studies, Johnson and coworkers combined graded light exposure with temperature and composition gradients to map and model the photopolymerization kinetics of acrylates, thiolenes and a series of co-monomer systems [40 2]. 

The DnPont photopolymeric system consists of polymeric binder resins, e.g. PVA, PMMA, cellnlose acetates and styrene-acrylates, reactive acrylic monomers, e.g. aryloxy or alkoxy acrylates, a dye sensitiser and a radical or charge transfer photoinitiator, e.g. DEAW and HABI respectively (see Chapter 4, section 4.5.2), and plasticisers. The process for producing the refractive index structures is as follows ... 

Following route A (Fig. 1), Yan Xiao et al. reported the chemoenzymatic synthesis of poly(8-caprolactone) (PCL) and chiral poly(4-methyl-8-caprolactone) (PMCL) microparticles [5]. The telechelic polymer diol precursors were obtained by enzymatic polymerization of the corresponding monomers in the presence of hexanediol. Enzymatic kinetic resolution polymerization directly yielded the (R)-and (S )-enriched chiral polymers. After acrylation using acryloylchloride, the chiral and nonchiral particles were obtained by crosslinking in an oil-in-water emulsion photopolymerization. Preliminary degradation experiments showed that the stereoselectivity of CALB is retained in the degradation of the chiral microparticles (Fig. 2). 

Fig. 2 Synthesis of acrylated chiral PMCL left) and microparticles (right) obtained from acry-lated polymers by oil-in-water emulsion photopolymerization [5]...

The published results concerning polymerization of acrylic acid or methacrylic acid in the presence of polyCethylene oxide) in water are controversial. Ferguson and Shah found that PEG with sufficiently high molecular weight increases the polymerization rate, while Kabanov at al found that in the presence of high molecular weight PEG the rate of polymerization of acrylic and methacrylic acids is lower than in blank reaction. Our results show that in the case of methacrylic acid photopolymerization in the presence of PEG of mol. weight 20,000, the rate of the reaction increases. This differences can be explained by the conditions of polymerization as well as methods used to follow the process different in both studies. 

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