Macromer

The study of acid-base interaction is an important branch of interfacial science. These interactions are widely exploited in several practical applications such as adhesion and adsorption processes. Most of the current studies in this area are based on calorimetric studies or wetting measurements or peel test measurements. While these studies have been instrumental in the understanding of these interfacial interactions, to a certain extent the interpretation of the results of these studies has been largely empirical. The recent advances in the theory and experiments of contact mechanics could be potentially employed to better understand and measure the molecular level acid-base interactions. One of the following two experimental procedures could be utilized (1) Polymers with different levels of acidic and basic chemical constitution can be coated on to elastomeric caps, as described in Section 4.2.1, and the adhesion between these layers can be measured using the JKR technique and Eqs. 11 or 30 as appropriate. For example, poly(p-amino styrene) and poly(p-hydroxy carbonyl styrene) can be coated on to PDMS-ox, and be used as acidic and basic surfaces, respectively, to study the acid-base interactions. (2) Another approach is to graft acidic or basic macromers onto a weakly crosslinked polyisoprene or polybutadiene elastomeric networks, and use these elastomeric networks in the JKR studies as described in Section 4.2.1. 

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). 

A copolymerizable group, such as an acrylate (R = H) or methacrylate (R = methyl), on one end of the molecule, and the high Tg polymer on the other end characterize the macromer. A chemically inert group, such as oxyethylene may be present to connect the two parts of the macromer. Macromers have been synthesized by different methods and some are commercially available. 

H. P. Wittmann, K. Kremer, K. Binder. Macrom Theory Simul 7 275, 1992. 

S. Kimura. New trends of membrane separation technology. Makromol Chem Macrom Symp 70-71 291, 1993. 

Macroinitiators 56 Macromers see Macromonomers Macromolecular monomers 157 Macromolecules, at-co difunctional 151 Macromonomers 21-23, 54-56, 155. 157... 

Merz A, Baumann R, Haimerl A (1987) Makromol. Chem., Macrom. Symp. 8 61... 

Liu B, Lewis AK, Shen W (2009) Physical hydrogels photo-cross-linked from self- assembled macromers for potential use in tissue engineering. Biomacromolecules 10 3182-3187 Vandermeulen GWM, Tziatzios C, Duncan R et al (2005) Peg-based hybrid block copolymers containing alpha-helical coiled coil peptide sequences control of self- assembly and preliminary biological evaluation. Macromolecules 38 761-769... 

When a single macromer is incorporated into a polymer chain, the result is a three armed star , as shown in Fig. 5.12 a). When numerous macromers are incorporated into a single backbone, the result is a comb , as shown in Fig. 5.12 b). In the case, where macromers are produced in situ, the macromers themselves can be branched and the resulting polymers can be branched in a complex fashion, as shown in Fig. 5.12 c). 

Figure 5.12 Examples of long chain branched molecules produced by macromer incorporation a) three-armed star b)"comb molecule,and c) complexly branched molecule...

It can be arranged that these oligomers contain a reactive end group, e.g., hydroxyl, carboxyl, allowing subsequently further polymerisation with a different reactant monomer to take place. These reactive oligomers are called macromers. 

Finally, some polymerisations can be directed such that the final oligomer or polymer contains two or more reactive end groups capable of extended polymerisation with different monomers. These materials are named telechelic macromers or telechelic polymers. 

Thermoset polymers (sometimes called network polymers) can be formed from either monomers or low MW macromers that have a functionality of three or more (only one of the reagents requires this), or a pre-formed polymer by extensive crosslinking (also called curing or vulcanisation this latter term is only applied when sulfur is the vulcanising or crosslinking agent.) The crosslinks involve the formation of chemical bonds — covalent (e.g., carbon-carbon bonds) or ionic bonds. 

J.C. Rodriguez-Cabello, J. Martin-Monge, J.M. Lagaron and J.M. Pastor, Macrom. Chem. Phys., 199... 

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