Monomers multifunctional

Low-molecular weight polymers + Vinyl monomers + Multifunctional vinyl monomers... 

An idealized formulation guideline showing possible interactions of single vinyl unsaturated monomers, multifunctional vinyl cross-linking molecules and polymeric materials is represented by Pig. 5. 

Network structures are induced by polymerization of bifunctional monomers. Multifunctional monomers give a greater number of network structures. Ethylene-glycolglyceroltriacetate shows a three-dimensional network structure by polymerization ... 

In some cases of multifunctional monomers the possibility exists for branches on branches, which ultimately result in cross-linked products and effectively infinite molecular weights well before p reaches unity. 

The fraction of unreacted B groups is rp, so this gives the probability of reaction for B. Since p is the fraction of A groups on multifunctional monomers, rp must be multiplied by 1 - p to give the probability of B reacting with an AA monomer. The total probability for the chain shown is the product of the probabilities considered until now ... 

The terminal B group reacts with an A group from a multifunctional monomer ... 

Our interest from the outset has been in the possibility of crosslinking which accompanies inclusion of multifunctional monomers in a polymerizing system. Note that this does not occur when the groups enclosed in boxes in Table 5.6 react however, any reaction beyond this for the terminal A groups will result in a cascade of branches being formed. Therefore a critical (subscript c) value for the branching coefficient occurs at... 

For a fixed extent of reaction, the presence of multifunctional monomers in an equimolar mixture of reactive groups increases the degree of polymerization. Conversely, for the same mixture a lesser extent of reaction is needed to reach a specified with multifunctional reactants than without them. Remember that this entire approach is developed for the case of stoichiometric balance. If the numbers of functional groups are unequal, this effect works in opposition to the multifunctional groups. 

In resists of this class, the imaging layer contains a multifunctional monomer that can form an intercormected network upon polymerization, and a photosensitizer to generate a flux of initiating free radicals. Although not stricdy required for imaging, the composition usually includes a polymeric binder (typically an acryhc copolymer) to modify the layer s physical properties. Figure 7b shows the chemical stmctures of typical components. 

Olefin isomerization can be catalyzed by a number of catalysts such as molybdenum hexacarbonyl [13939-06-5] Mo(CO)g. This compound has also been found to catalyze the photopolymerization of vinyl monomers, the cyclization of olefins, the epoxidation of alkenes and peroxo species, the conversion of isocyanates to carbodiimides, etc. Rhodium carbonylhydrotris(triphenylphosphine) [17185-29-4] RhH(CO)(P(CgH )2)3, is a multifunctional catalyst which accelerates the isomerization and hydroformylation of alkenes. 

Resin-modified glass—ionomer lining and restorative materials add a multifunctional acidic monomer to the poly(acryhc acid) [9003-01 Hquid component of the system. Once the glass powder and Hquid are mixed, setting can proceed by the acid—glass—ionomer reaction or the added monomer can be polymerized by a free-radical mechanism to rapidly fix the material in place (74,75). The cured material stiH retains the fluoride releasing capabiHties of a glass—ionomer. 

The polybenzoxazines (PBZs) provide a new class of phenolic resins that were first described by Ishida in 1998 (Ref. 15). Synthesis of the resins involves three components a phenol, a primary amine and formaldehyde. The first stage involves the formation of a multifunctional benzoxazine monomer Figure 23.30 a)). The monomer can then be ring-opened at elevated temperatures (160-220 C) to yield a polymeric stmcture (Figure 23.30(b)). 

Carboxylic acids with multifunctional epoxides or epoxy functional monomers... 

It may also be possible to crosslink the acrylic PSA with the help of multifunctional acrylates or methacrylates [87], These monomers can simply be copolymerized with the balance of the other monomers to form a covalently crosslinked network in one step. Since the resulting polymer is no longer soluble, this typ)e of crosslinking is typically limited to bulk reactions carried out as an adhesive coating directly on the article or in emulsion polymerizations where the crosslinked particles can be dried to a PSA film. 

As mentioned previously, the use of multifunctional monomers results in branching. The introduction of branching and the formation of networks are typically accomplished using trifunctional monomers, and the average functionality of the polymerization process will exceed 2.0. As the average functionality increases, the extent of conversion for network formation decreases. In... 

Interesting TPEs can be derived from binary and ternary blends of polyfunctional acrylates, ACM, and fluorocarbon rubber (FKM) [53]. During the blend preparation, the liquid multifunctional acrylate monomer used is polymerized and forms the continuous matrix encapsulating the... 

Citric acid is a nontoxic metabohc product of the body (Krebs or citric acid cycle), and it has been approved by FDA for its use in humans. It was found that the citric acid can be reacted with a variety of hydroxyl-containing monomers at relatively mUd conditions. " Citric acid can also participate in hydrogen bonding interactions within a polyester network. Citric acid was chosen as a multifunctional monomer to enable network formation. 

PAMAM dendrimers are synthesized in a multistep process. Starting from a multifunctional amine (for example ammonia, ethylenediamine, or tris(2-amino-ethyl)amine) repeated Michael addition of methylacrylate and reaction of the product with ethylenediamine leads to dendrimers of different generation numbers [1,9]. Two methylacrylate monomers are added to each bifunctional ethylenediamine generating a branch at each cycle. Unreacted ethylenediamine has to be completely removed at each step to prevent the initiation of additional dendrimers of lower generation number. Excess methylacrylate has also to be removed. Bridging between two branches of the same or of two different dendrimers by ethylenediamine can also be a problem, and has to be avoided by choosing appropriate reaction conditions. 

Phenol, the simplest and industrially more important phenolic compound, is a multifunctional monomer when considered as a substrate for oxidative polymerizations, and hence conventional polymerization catalysts afford insoluble macromolecular products with non-controlled structure. Phenol was subjected to oxidative polymerization using HRP or soybean peroxidase (SBP) as catalyst in an aqueous-dioxane mixture, yielding a polymer consisting of phenylene and oxyphenylene units (Scheme 19). The polymer showed low solubility it was partly soluble in DMF and dimethyl sulfoxide (DMSO) and insoluble in other common organic solvents. 

The basic principle of the light-induced polymerization of multifunctional monomers can be represented schematically as follows ... 

The photoinitiator selected for this study was 1-benzoyl cyclohexanol (Irgacure 184 from Ciba Geigy), a compound known for its high initiation efficiency and the weak coloration of its photoproducts. The multifunctional monomer was an epoxy-diacrylate derivative of bis-phenol A (Ebecryl 605 from UCB). A reactive diluent, tripropyleneglycol diacrylate, had to be introduced in equal amounts, in order to lower the viscosity of the formulation to about 0.3 Pa.s. 

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