MACROMER functional groups

MACROMER (10) is a trademark by CPC International of a new family of monomers. Because they are synthesized via anionic chemistry, their molecular weight is controlled by the ratio of monomer to initiator and they also have very narrow molecular weight distributions. The typical polymeric portions of MACROMEHf that have been investigated are polystyrene, polydiene, and blocks of the two (5, lCi). Some of the typical MACROMER functional groups that were examined are shown in Figure 8. These are shown to indicate the wide variety of functional groups that are useful for various polymerization mechanisms (4). 

Block copolymers are also produced using such macromers. Again, the various units of the polymer can be designed to act as needed with hard or/soft, or hydrophilic or hydrophobic, or other combinations. In addition, these macromers generally have two active functional groups that allow polymerization to occur. 

Macromers can also be used as cross-linkers between already formed polymers when both ends are active. These functional groups could be either two vinyl ends or two Lewis acids or bases such as two hydroxyl or amine groups. Interpenetrating polymer networks (IPNs) and related structures such as dendrites and stars can also be formed using macromers. 

Figure 5. Theoretical relationship between required degree of capping and Mn for star-like macromers having (A) 3, (B) 4, and (C) 5 functional groups. (Note For HPL having 1.3 OH groups Cg on the average, and a molar substitution of 1.0.)...

The best test for functionality would be in a copolymerization study. A polystyrene with a methacrylate terminal functional group was prepared. A review of relative reactivity ratios indicated that vinyl chloride reacts very rapidly with methacrylates. Therefore, a copolymerization of the polystyrene terminated with a methacrylate functional group in vinyl chloride would be a good test case, and one should observe the disappearance of the MACROMER if the reaction is followed by using GPC analysis. 

Functionally terminal polymers are valuable material intermediates. The di- and polyfunctional varieties (telechelic polymers) have found theoretical (e.g., model network) and commercial (e.g., liquid rubber) applications (1, ). On the other hand, macromolecules with a functional group at one chain end (semitelechelic polymers) have been used to prepare novel macromolecular monomers (Macromers ), as well as block and graft copolymers ( -8). 

The synthesis of novel initiators and the ROP of existing or new monomers and macromers substituted with functional groups provide a very interesting and promising strategy for producing structurally advanced macromolecules. 

In the above example, both 50 and 51 are MACROMERS . The cyclic ammonium group of 50 can also be transformed into several other functional groups, for example 48) ... 

Transfer reactions are utilized to regulate molecular mass of polymerizing macromolecules, for grafting, and to introduce functional groups into the chains of polymeric monomers , the macromers. 

By reactions (82)-(84), 8 wt. % Br was introduced into the oligomers, an average of 1.95 Br atoms per chain. This work was extended by Kennedy and Smith [91] who selected the co-initiator from a group of transfer agents, which thus had a double function. This new technique they called the inifer method (from co-initiator-trans/er agent). When the rate of transfer to monomer is much less than to the inifer, the formation of the reactive macromer end groups can be better controlled. Macromer formation can be represented by the scheme... 

Methacrylate-substituted POSS macromers have been made that contain one polymerizable functional group. These macromers have been both homopolymerized and copolymerized (Fig. 8a). Propyl methacrylate-substituted POSS monomers 9 and 10, containing seven nonreactive cyclohexyl and cyclopentyl groups, respectively, are examples. SolubiUty differences between the MA-POSS monomers 9 and 10 were observed in THF, toluene, and benzene. The cyclohexyl-substituted MA-POSS 9 has approximately twice the solubility of the cyclopentyl-substituted MA-POSS 10. Furthermore, monomer 9 displayed a broad two-step thermal transition beginning at 187°C, which involves melting, thermal polymerization and decomposition, whereas 10 gave a similar thermal transition beginning at 192°C. X-ray... 

Chemical hydrogels are 3D crosslinked networks that formed by new covalent bonds between water-soluble macromers. To use chemical hydrogels for biomedical application, chemical reactions should not damage incorporated biopharmaceuticals or cells. There are several chemical crossUnking methods such as redox-initiated polymerization, photopolymerization, classical organic reactions between functional groups, and enzymatic reactions. 

A second test was done by using butyl acrylate as the comonomer as shown in Figure 11. The reactivity ratios in this case are such that the methacrylate functionality would react slower with acrylates than with vinyl chloride. As predicted the butyl acrylate is at 62% conversion before the MACROMER peak is significantly diminished. These data add validity to the hypothesis that the placement of side chains in the backbone is dependent on the terminal group of the macromonomer and the relative reactivity of its comonomer. 

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