Macromonomers graft copolymers

Keywords. Poly(macromonomers), Graft copolymers, Comb, Star, Brush, Polymeric microspheres... 

Macromonomers always lead to the formation of graft copolymers. For example, the vinyl-terminated polystyrene can be copolymerized with ethylene to produce a graft copolymer of polyethylene, whereby the vinyl moiety of polystyrene is integrally polymerized into the linear polyethylene backbone ... 

PDMS macromonomer was used as a component of block segment to obtain a graft block copolymer with PMMA (Scheme 1) [51-53]. This graft block copolymer is characteristic of surface water repellence, easy peeling, and weatherability superior to simple graft copolymers of the same members. PDMS-b-PVC film also shows long life surface water repellency with weatherability and very low coefficiency of abrasion [18,54]. 

In the case of polymerization of monosubstituted monomers S, RA) with 66-68, copolymerization of the macromonomer to form a graft copolymer is a significant side reaction.76... 

Interestingly, the first example of a macromonomer, long before the names Macro-mer or macromonomer have been coined 94), is a styrene terminated polydimethyl-siloxane synthesized by the reaction of a Grignard derivative of p-ch loro styrene and an co-chlorodimethylsiloxane oligomer 90) as shown in Reaction Scheme IX. Later, these macromonomers have been reacted with different vinyl monomers such as styrene and acrylates, and relatively well defined graft copolymers have been synthesized. 

The synthesis of PDMS macromonomers with vinyl silane end-groups and their free-radical copolymerization with vinyl acetate, leading to poly(vinyl acetate)-PDMS graft copolymers, was described 346). The copolymers produced were later hydrolyzed to obtain poly(vinyl alcohol)-PDMS graft copolymers. 

Recently it has been shown that anionic functionalization techniques can be applied to the synthesis of macromonomers — macromolecular monomers — i.e. linear polymers fitted at chain end with a polymerizable unsaturation, most commonly styrene or methacrylic ester 69 71). These species in turn provide easy access to graft copolymers upon radical copolymerization with vinylic or acrylic monomers. 

The chief application of macromonomers is, however, to provide easy access to graft copolymers 69,70,71,84,851 by free radical copolymerization with a vinylic or acrylic comonomer. This grafting through process offers graft length control and provides randomness of graft distribution. 

Graft copolymers can also be made by free radical copolymerization of a macromonomer with an acrylic or vinylic comonomer, as mentionned earlier 69-71>. 

The purpose of this review is to show how anionic polymerization techniques have successfully contributed to the synthesis of a great variety of tailor-made polymer species Homopolymers of controlled molecular weight, co-functional polymers including macromonomers, cyclic macromolecules, star-shaped polymers and model networks, block copolymers and graft copolymers. 

In our own research, the functional termination of the living siloxanolate with a chlorosilane functional methacrylate leading to siloxane macromonomers with number average molecular weights from 1000 to 20,000 g/mole has been emphasized. Methacrylic and styrenic monomers were then copolymerized with these macromonomers to produce graft copolymers where the styrenic or acrylic monomers comprise the backbone, and the siloxane chains are pendant as grafts as depicted in Scheme 1. Copolymers were prepared with siloxane contents from 5 to 50 weight percent. 

Fig. 16 The thermal response of different polymeric structures based on PVCL and the amphiphilic macromonomer MAC11EO42. Left Shrinking of the grafted PVCL microgel. Right Heat-induced aggregation of the graft copolymer and formation of a mesoglobule [181]...

The plots of h/h vs. copolymer concentration also reveal differences in the micropolarity of the hydrophobic domains created upon association of the various copolymers in water. A qualitative assessment of this property is given by the h/h value determined in the copolymer solutions of highest concentration when the plateau value is attained (Fig. 25). This value depended significantly on the grafting level the solution of the most densely grafted copolymer yielded the lowest h/h value (1.40) and the pure homopolymer the highest. In all cases, this value is higher than the value (1.20) recorded for micellar solutions of the macromonomer. It can be concluded... 

If the DC photoiniferter having a polymerizable double bond, i.e., a monomer iniferter, is successively used as both monomer and iniferter, macromonomers and graft copolymers would be obtained according to Eq. (54) [188] ... 

The photopolymerization of St with catalytic amount of 52 as the pho-toiniferter gave a benzene-soluble polymer that contains a styryl double bond and a DC group at the polymer chain ends. When this macromonomer-iniferter 54 was copolymerized with a second monomer in the presence of an azo initiator, the formation of a high molecular weight graft copolymer was confirmed by GPC data. The monomer iniferter 52 was also used for the preparation of photoresist polymers [189]. 

Recently, well-defined graft copolymers have been prepared by living radical polymerization using macromonomers [262]. 

The reaction scheme is very general, but control over the extent of the intermolecular reactions and the distribution of the number of arms in the star is limited. The arm first method includes the polymerization (to form star polymers) or copolymerization (to form comb or graft copolymers) of macromonomers. The technique provides a handy simplification if the arm MW need not be very high and the MW control of the branched polymers is not very important. 

The completely cationic synthesis of comb or graft copolymers have yet to be realized [103]. However, numerous backbone polymers, branches and macromonomers have been prepared separately via cationic polymerization and these have been combined with other grafting and polymerization processes to prepare (co)polymers that cannot easily be prepared otherwise [103]. 

Last but not least, some of us have recently synthesized polyimide-aliphatic polyester triblock and graft copolymers in collaboration with Hedrick and his coworkers [ 97,98]. Well-defined aminophenyl or diaminophenyl end-functional polyester oligomers have been synthesized on purpose and used as end-cappers or macromonomers leading to the aforementioned triblock or graft copolymers, respectively. The polyimide-polyester copolymers so obtained proved to be highly efficient promoters of polyimide nanofoams (for more details see Sect. 4.2). 

The next step concerned the synthesis of the polyester-polyimide copolymers. Triblock copolymers have been prepared by a step-growth copolymerization of stoichiometric amounts of an aromatic diamine and dianhydride (e.g., PMDA and 3FDA, as depicted in Scheme 41a) added with the single oo-amino polyesters as chain end-cappers. Graft copolymers can be prepared as well. In this case, the diamine end-functionalized oligomeric macromonomers are copolymerized with the polyimide condensation comonomers (Scheme 41b). 

Macromonomers containing a norbornene group have been polymerized by ROMP (Sec. 7-8) to form graft copolymers [Breunig et al., 1995 Heroguez et al., 1997]. 

Graft copolymers were prepared by both classical strategies, i.e., from enzymatically obtained macromonomers using subsequent chemical polymerization and by enzymatic grafting from hydroxy-functional polymers. 

Kalra et al. studied the synthesis of PPDL graft copolymers following route A as shown in Scheme 6. The macromonomers were obtained by the enzymatic ROP of PDL from HEMA and PEGMA [49]. In a comparative study, Novozym 435 was found to be the most active biocatalyst for this reaction step. Subsequently, graft copolymers were obtained by free-radical polymerization of the macromonomers. A similar approach was published by Srivastava for the HEMA-initiated enzymatic ROP of CL and subsequent free-radical polymerization [50]. 

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