Macromer structures

The preferred polyether used in this reaction is a higher molecular weight triol of 5000-6000 daltons (preferred MW is 6000 daltons). By copolymerisation of the macromer (structure 6.12) with ACN and styrene, a NAD is obtained in situ, which is in fact a graft copolymer ... 

It was observed experimentally that the trans isomer of maleic structures the fumaric ester structures, are more reactive in copolymerisation with ACN and styrene than the maleic esters. The maleic esters (cis isomers, of structure 6.12) were rearranged to form fumaric esters (trans isomers, of structure, shown in Figure 6.4), in the presence of specific catalysts such as calcium salts of organic acids (calcium naphthenate [55], calcium octanoate [55]) or morpholine [55]. The resulting very efficient and reactive macromer structure of the fumaric ester type is shown in Figure 6.5. 

A very convenient method to obtain a macromer (structure 6.13) is by using an unsaturated isocyanate [50] or by using some accessible raw materials, by the reaction of a hydroxy alkyl acrylate or methacrylate with one -NCO group of a diisocyanate for example, 2,4 toluene diisocyanate (TDI) and to react the remaining -NCO group with the terminal hydroxyl group of a polyether polyol ... 

Earlier, successful attempts at physically crosslinking acrylic PSAs have been disclosed in the work of Husman et al. [98], Mancinelli and colleagues [99,100] and others. Instead of making ABA type structures, these authors studied and developed the use of high macromers in acrylic copolymers. Macromers are... 

Common examples of the high Tg macromers are based on polystyrene or polymethylmethacrylate (PMMA) polymers of sufficiently high molecular weight to have a high T (typically on the order of 70-100°C as measured by differential scanning calorimetry) and also to make them immiscible with the acrylic polymer backbone once the solvent or heat has been removed. Typical molecular weight of the polystyrene or PMMA macromers is on the order of 5000-10,000 Da. Their generic structure can be pictured as in Fig. 13 (shown there for polystyrene). 

Macromers have been used to produce thermoplastic elastomers. Generally, the backbone serves as the elastomeric phase while the branches serve as the hard phases. These structures are often referred to as comb -shaped because of the similarity between the rigid part of the comb and its teeth and the structure of these graft polymers. 

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. 

A more recent development, MACROMER , a new tool that expands our capability for synthesizing controlled polymer structures, will also be discussed. 

A polystyrene with a functionality such as a methacrylate group copolymerized with a mixture of ethyl and butyl acrylate should yield a graft structure meeting the criteria of a thermoplastic elastomer as shown in Figure 13. The data in this figure show that as the MACROMER content is increased, the tensile... 

The use of MACROMER technology is another synthetic tool that the polymer scientist has in being able to prepare a wide variety of new types of polymer structures which could be of some potential commercial interest, such as ... 

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. 

The cyclic tin alkoxides have the additional advantage of offering a convenient synthetic pathway for the synthesis of macromers, triblock, and multiblock copolymers [81,82]. Macromers from l-LA [83],e-CL [84], and l,5-dioxepan-2-one (DXO) [85] have been synthesized as well as triblock poly(L-LA-b-DXO-b-L-LA) [86] and multiblock copoly(ether-ester) from poly(THF) and e-CL [87]. The polymerization proceeds by ring expansion and the cyclic structure is preserved until the polymerization is quenched by precipitation. 

The preparation of prepolymers [111] or macromers with functional end groups, so called telechelic polymers, is another approach to structurally unconventional architecture. The functional end groups are introduced either by functional initiation or end-capping of living polymers, or by a combination of the two. In this way, monomers that are not able to copolymerize can be incorporated in a copolymer. Telechelic prepolymers can be linked together using chain extenders such as diisocyanates [112]. In this process, it is essential that the structure and end groups of the prepolymers can be quantitatively and qualitatively controlled [113]. 

The above thermal analysis studies demonstrated the enhanced thermal stability of POSS materials, and suggested that there is potential to improve the flammability properties of polymers when compounded with these macromers. In a typical example of their application as flame retardants, a U.S. patent39 described the use of preceramic materials, namely, polycarbosilanes (PCS), polysilanes (PS), polysilsesquioxane (PSS) resins, and POSS (structures are shown in Figure 8.6) to improve the flammability properties of thermoplastic polymers such as, polypropylene and thermoplastic elastomers such as Kraton (polystyrene-polybutadiene-polystyrene, SBS) and Pebax (polyether block-polyamide copolymer). 

It should be noted that the inconsistency in the flammability performance of various types of poly-mer/POSS hybrid systems could be ascribed to several factors, such as, the type of polymeric material, the structure of POSS macromer, and the degree of dispersion of POSS in the polymer matrix. 

One of the older methods to obtain macromers is to add very small quantities of a monomer having a double bond and a polymerisable epoxy group in the same structure to propylene oxide, during the anionic polymerisation. A typical example of such a kind of monomer is allyl glycidyl ether. This monomer copolymerises anionically with PO, giving polyethers with small quantities of lateral double bonds (reaction 6.10). 

Figure 6.4 The structure of ternary copolymer ACN-styrene-maleic anhydride macromer, a NAD generated in situ by radical copolymerisation...

Figure 6.5 Macromer with fumaric ester structure...

MW of 120,000 daltons) [61]. In fact the nonreactive NAD presented before (structures 6.15 and 6.16) are poly ethers with extended molecular weight, the chain extender being the epoxy resins or the diisocyanates (or polyisocyanates). As in the case of macromers, it is possible to obtain high, solid stable polymeric dispersions, of low viscosities, with nonreactive NAD too. 

Figure 3 Physical crosslinks in the PLGA-PEG-PLGA in water (ReGel ) showing hydrophobic domain structures (Courtesy of Macromed, Inc., Sandy, UT.)...

Eder, G. Janeschitz-Kriegl, H (1997). Structure development during processing 5 Crystallization. Material Science and Technology, vol. 18 Weinheim H.E.N. Meijer ed. Elmoumni, A. Gonzalez-Ruiz, R.A. Coughlin, E.B. Winter H.H. (2005). Macrom. Chem. 

Living polymerization created the idea of Macromer (proposed by R. Milkovich, generic term is macromonomer) for synthesizing a graft copolymer of well-controlled structure. We reported the synthesis of polydimethylsiloxane (PDMS)... 

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