Difunctional acrylic monomers

Eaton DF, unpublished results for a photopolymer composition containing 5wt% initiator, 35 wt% difunctional acrylate monomer, and a polymethacrylate binder. The composition was washed out after exposure to ultraviolet light through a step wedge that is, the photopolymer functioned as a negative resist... 

Novel difunctional acrylic monomers and multifunctional acrylic oligomers with a propensity for intra-intermolecular addition polymerization (cyclopolymerization) have been conveniently synthesized from conventional acrylates or diacrylates and paraformaldehyde under neat conditions using l,4-diazabicyclo[2,2,2]octane (DABCO) as the catalyst (7-5). 

It was assumed that three monomers would be used in this stndy methyl methacrylate, butyl acrylate and styrene. The possiblity of using styrene seemed to he especially interesting because of its very low cost compared to the other monomers. The other two monomers were selected for the significant differences in their polarity and solnhility in water that might affect the particle morphology and the T of poly(methyl methacrylate) and poly(butyl acrylate). Difunctional acrylate monomer (1,4-hntanediol dimethacrylate) was also used in some experiments since it encouraged the formation of an IPN strncture. 

A typical EB curable formulation will generally consist of a relatively high molecular weight solid or semi-solid difunctional acrylic resin reduced to application viscosity with combinations of liquid mono- and multifunctional acrylic monomers. These acrylic monomers, along with a few other selected polymerizable monomers, serve as reactive diluents and allow formulation of solvent-free compositions. Usually, small amounts of additives are also used in order to provide special properties, such as slip. 

Sequential polymerization of two acrylic monomers was discussed in Sections VI.E.4, VI.E.7 and VI.F. This technique was extended to three comonomers with formation of ABC-type triblock copolymers. For example, PMMA-fcZoc -PtBMA- Zoc -PMMA triblock copolymer was synthesized by the sequential DPFlLI-initiated polymerization of MMA, tBMA and MMA, respectively . Symmetrical BAB-type diblock copolymers were also prepared in two steps, polymerization of the A monomer being first initiated by a difunctional compound. The B blocks formed in the second step necessarily have the same average degree of polymerization. 

Matyjaszewski et al. showed, however, that when a Cu(I)Br catalyst was used in conjunction with bromine-based initiators for a similar system (St/tBA), the polymerizations were well controlled and chain extension in either direction was possible [194]. This is different from the nitroxide system where chain extension of a pSt macroinitiator with acrylate monomers resulted in low blocking efficiency [71 ]. AB and ABA type block copolymers were prepared using monofunctional and difunctional ptBA or pSt macroinitiators. Deprotection of the ferf-butyl esters in these AB block copolymers afforded amphiphilic block copolymers capable of being used as surfactants for emulsion polymerizations [194,195]. 

The photoinitiated cationic polymerization of liquid epoxidized polyisoprene is an efficient method to generate rapidly crosslinked elastomers. In the presence of a triarylsulfonium salt, the reaction develops readily upon UV exposure, with formation of both inter and intramolecular ether linkages. The formulation reactivity can be substantially enhanced by the addition of a difunctional vinyl ether or acrylate monomer, which acts as a reactive diluent and leads to the formation of an... 

By far the acrylates are the monomers of choice in UV curable systems. Not only do they cure at extremely rapid rates compared to other monomer systems (acrylic > methacrylic > vinyl > allylic), but they are also available in a wide range of structures which are monofimctional, difunctional, trifunctional, and tetrafunctional. Additionally, as shown in the oligomer section, acrylates can be used to derivatize oligomers or pre-polymers. Commonly in UV curable formulations it is necessary to use a number of monomers in order to achieve a balance between speed of cure and properties of the final film. It is not unheard of to use four or five monomers in a single UV curable formulation. For instance, tri- and tetra-functional acrylates result in highly crosslinked films when incorporated into UV curable resins however, they severely limit the extent and rate of the curing process. Thus, one often combines a tetrafunctional acrylate to increase crosslink density with a mono and/or difunctional acrylate to increase the cure rate. 

Coating technique This technique usually deposits a hydrophilic layer such as HEC, polyvinyl alcohol, CS, polyacrolein, and polyethylenimine on a hydro-phobic one [13,85,105,106]. The coating layers prepared are however not durable and stable and can be easily leached out. To overcome this drawback, the membranes (PVDF, PES, PTFE, polycarbonate, nylon) are coated with a mixture containing a functional monomer (hydroxyalkyl acrylate or methacrylate), a polymerization initiator (ammonium or potassium persulfate), and a cross-linking agent (difunctional acrylates, methacrylates, or acrylamides) and exposed to radical polymerization initiated by heating, UV, or y-radiation [86]. 

Figure 4. Synthesis of highly fluorinated difunctional acrylic vinyl monomers.

The gel polymer network strucmre can be varied to that of combs and ladders by changing a kind of acrylate monomer. It also is possible to make an ion-conductive gel with a polyethylenic strucmre by cross-linking a difunctional acrylate compound such as polyethylene-glycol-diacrylate. Valence Inc. was not able to commercialize this battery, although it was proceeding with the development of polymer batteries that combined VjOg positive electrode and lithium metal negative electrode by this electrolyte. Table 21.1 shows the ionic conductivities of various gel polymer electrolytes. 

Rolla et ah, used microwave dielectric measurements to monitor the polymerization process of mono functional n-butyl acrylate as well as 50/50 w/w blends with a difunctional hexane-diol diacrylate that gave highly cross-linked networks. In these real time cure experiments the decreasing acrylate monomer concentration was studied via a linear correlation with the dielectric loss index at microwave frequencies. This correlation is a result of the largely different time scales for dipolar polarization in the monomer on one hand and in the polymerized reaction product on the other hand. 

Typical monomers are of the polymerizable plasticizer type based on functionally active acrylates. A difunctional acrylate (Fig. 12.8) would be used for chain-extension purposes, whilst a trifunctional one (Fig. 12.9) would be primarily used to control crosslink density and hence cure state. Both would have low viscosity, approximately 100 cps, and hence during processing act as plasticizers. 

Most of the dental composite resin materials and denture-base polymers are diluted with the less viscous difunctional acrylates. These are the met-hacrylic monomers of which EGDMA, DEGDMA, triethylene glycol dimethacrylate (TREGDMA) (Fig. 3) and 1,4-butanediol dimethacrylate (BUDMA) (Fig. 4) are the most widely used (Table 2). The use of acrylates in dentistry is an expanding field. Some are... 

The polymerization of acrylic and methacrylic anhydride is interesting because linear polymers can be obtained in contrast to the cross-linked networks usually formed from difunctional vinyl monomers [588-590]. In a cyclopolymerization reaction, alternating... 

Although the precise composition of relevant commercial formulations has not been disclosed by the manufacturers, it is generally agreed that in most cases acrylate- and methacrylate-based monomers are used as polymerizable components [314]. In typical holographic storage studies, the formulation comprises a difunctional acrylate oligomer, N-vinyl carbazole, and isobomyl acrylate [325]. In... 

The principal monomers butadiene, styrene, vinyl acetate, (meth)acrylates and acrylonitrile essenhally determine the material properties of films made from the corresponding dispersions the glass transition temperature, the water absorption capacity, the elasticity, etc. Auxiliary monomers, which are only used in a small proportion, usually <5 %, control important properties such as colloid-chemical stabilization (acrylic acid, methacrylic acid, acrylamide, methacrylamide), crosslinking within the particles (difunctional acrylates, divinylbenzene, etc.) or hydrophilic properties (OH-containing monomers, such as hydroxyacrylates). Reactive monomers which still contain a latently reactive group even after incorporation into the polymer, for example glycidylmethacrylate or N-methylol(meth)acrylamide, can form a network between various particles and polymer molecules after film formation. 

The fact that crosslinking proceeds at considerably high conversions of the monomers (50%) and at copolymerization temperatures > 60 °C is a distinctive feature of this system, as compared with systems containing other unsaturated derivatives of acrylic acids, which is determined by the difunctional nature of 10. 

Since each acrylate group is difunctional, the diacrylates are tetrafunctional while the triacrylates are hexafunctional. For polymerization ofthe polyfunctional monomers at sufficiently high degrees of conversion, the branching must result in the formation of cross-links to give a three-dimensional network. 

The curing reaction of acrylates is typical of vinyl monomers. Therefore, the degree of double-bond conversion is the measure of the degree of cure. The best results are obtained when using oligomers as binders and monomers as reactive thinners. Examples of difunctional and polyfunctional acrylates are in Table 4.4. A partial list of the most common acrylate oligomers is below. - ... 

Allyl methacrylate and allyl acrylate are difunctional monomers, triallyl phosphate is a trifunctional monomer, and polyethylene glycol dimethacrylate is a polyfunctional monomer. All these lead to cross-linked graft copolymers. 

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