Monomer trifunctional

Hyperbranched polyurethanes are constmcted using phenol-blocked trifunctional monomers in combination with 4-methylbenzyl alcohol for end capping (11). Polyurethane interpenetrating polymer networks (IPNs) are mixtures of two cross-linked polymer networks, prepared by latex blending, sequential polymerization, or simultaneous polymerization. IPNs have improved mechanical properties, as weU as thermal stabiHties, compared to the single cross-linked polymers. In pseudo-IPNs, only one of the involved polymers is cross-linked. Numerous polymers are involved in the formation of polyurethane-derived IPNs (12). 

In the case of trifunctional monomers the situation is more complex. From the schematic diagrams (Figure 2.26) it will be seen that the polymers have more functional groups than the monomers. 

Figure 8.13. Schematic diagram of a trifunctional monomer (a) and its dimer (b) and trimer (c). The monomer has three reactive points and the dimer and trimer four and five respectively. In general, an...

Figure 8.14. Typical curve for viscosity against time of condensation of essentially trifunctional monomer systems under isothermal conditions...

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... 

Triethylene diamine (TEDA), 230, 231 Triethyl phosphate (TEP), 354 Trifluoroactic anhydride, 78 Trifhioromethanesulfonic acid, 334 Trifunctional monomers, 14 Triglyceride content, in resins, 60 Trihydroxymethylphenol curing process, 410... 

In all calculations the molar masses given in the top of Table I were used. First of all, the effects of variations in the concentration of trifunctional monomers were determined, as exemplified by the nine formulations of Table I and the resulting prepolymer characteristics after full conversion given in Table II. Formulations FIO to F40 result in branched prepolymers, which are cured in the third stage by difunctional monomers. On the other hand, formulations FOO to F04 result in the same linear prepolymer, which is subsequently cured with various mixtures of di- and trifunctional monomers. The number average functionalities of PI (and P2) and of the mixtures of E and F monomers are varied systematically between 2.0 and 2.4. Therefore, the only difference between formulations FjO and FOj is the stage in which the branching units are added. 

The prepolymer characteristics at the end of stages 1 and 2 are collected in Table II. Both the molecular mass and functionality distributions become wider in the second stage, in particular upon increasing the content of trifunctional monomer in the prepolymer. 

The weight fraction of o -mer calculated according to Eq. (36) for a trifunctional monomer is shown in Fig. 69 for several degrees of reaction. The curves resemble those for the polymers of an A—R—B2 monomer shown in Fig. 66, with the important difference that they do not vanish into the axis at a = ac. This is simply a consequence of the fact that condensation is far short of completion at the critical point. 

Fig. 69.—Weight fraction distribution for a branched polymer prepared from a simple trifunctional monomer at the a s indicated. ...

Step growth polymerization can also yield highly crosslinked polymer systems via a prepolymer process. In this process, we create a prepolymer through a step growth reaction mechanism on two of the sites of a trifunctional monomer. The third site, which is chemically different, can then react with another monomer that is added to the liquid prepolymer to create the crosslinked species. We often use heat to initiate the second reaction. We can use this method to directly create finished items by injecting a mixture of the liquid prepolymer and additional monomer into a mold where they polymerize to create the desired, final shape. Cultured marble countertops and some automotive body panels are created in this manner. 

Table 5.1 Reaction states of units of a trifunctional monomer characterized by the number of reacted groups and their assignment to various structure elements in a system undergoing crosslinking...

In a wider sense, functionality distribution also means combination of reactive groups of one kind (for instance, hydroxy, or carboxyl, or isocyanate groups) of higher and lower reactivity in one precursor molecule. By this combination, the network build-up can be effectively controlled. For instance, one less reactive A group out of three in a trifunctional monomer in a RA3 + R B2 system promotes chain extension in contrast to branching and shifts the gel point to higher values [30],... 

In nature, polycondensations of trifunctional monomers having two different functional groups occur under enzymatic control, resulting in tree-shaped, highly branched, but still soluble, macromolecules. 

Fig. 20. Plot of the exponent ras a function of the chain lengths between two branching points. Open symbols results by Colby et al. [118,119] for branched polyesters. The variation of this length was achieved by co-condensation of trifunctional monomers with increasing fraction of bifunctional units. Filled symbols refer to polydicyanurates (N Nj ), anhydride cured phenyl monoglycidyl ether with a small fraction of bisphenol A diglyci-dylether as crosslinker (N=8Nj ) and end-functionalized 3-arm polystyrene stars crosslinked by diisocyanate (N 40 N ). N denotes the number of repeating units between two branching points...

Acrylate Monomer/NVP. To observe the interaction between monomers, we compared the behavior of two monomer mixtures, I and T. These mixtures contrast the interaction of NVP and a monofunctional acrylate (IBOA), which should yield to linear polymerization, with a trifunctional monomer (TMPTA) which results in a crosslinked network. 

Note 4 Ethene and ethylene glycol are examples of difunctional monomers, glycerof is an example of a trifunctional monomer, and divinylbenzene and pentaerythritol are examples of tetrafunctional monomers. 

Hydrolytic polycondensation of trifunctional monomers of the type XSiYj leads to cross-linked three-dimensional as well as network and cis-syndiotactic (ladder-type) polymers, (XSiOj 5) With increasing amount of solvent, however, the cor-... 

Co-condensation of Organosilicon Trifunctional Monomers and/or Oligomers of Different Structure and Composition... 

In most cases, the mechanism of the polycondensation of trifunctional monomers XSiYj bearing a different substituent X is also different which is evident from the type and yield of linear, cyclic and polycyclic siloxanes formed as intermediates in the course of the corresponding polycondensation. 

Trifunctional monomers constitute an important class of monomers. One often encounters such reactants in which the various functional groups have different reactivities. Thus, the polyesterification of glycerol (VII) with phthalic anhydride proceeds with incomplete... 

As mentioned previously, the behavior of systems containing bifunctional as well as trifunctional reactants is also governed by the equations developed above. The variation of wx for the polymerization of bifunctional monomers, where the branching coefficient a is varied by using appropriate amounts of a trifunctional monomer, is similar to that observed for the polymerization of trifunctional reactants alone. The distribution broadens with increasing extent of reaction. The effect of unequal reactivity of functional groups and intramolecular... 

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. 

To complete the theoretical framework, we treat now characteristic examples which also demonstrate the full power of the cascade theory. This case is once again the polyconden-sation of trifunctional monomers with unlike functional groups1055. Another example is the random co-condensation of an f-functional monomer RAf and a bifunctional RB2 monomer, which is treated in the next chapter. All other cases can in principle be reduced to these general examples. 

Other allyl monomers of commercial significance are diallyl fumarale and diallyl malcate. These highly reactive trifunctional monomers contain two types of polymerizable double bonds. 

III. Intermediate Hydrolysis Products from Trifunctional Monomers. 444... 

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