142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

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172 K. Ito, S. Kawaguchi Fig. 8. Schematic representation of the possible conformations of adsorbed (co)polymers prepared using macromonomer technique: a brush adsorption of graft copolymer; b terminally-attached adsorption; c the mushroom-brush transition for strongly overlapping chains proposed by de Gennes [130] and Alexander [155] 100% macromonomer is copolymerized to attach onto their latex surface. However, this is not the case for styrene copolymerization with PEO macromonomers in which only 10% PEO macromonomer was copolymerized [112]. In contrast, it was confirmed that 100% of PEO macromonomers were copolymerized for the MMA and BMA dispersion copolymerization [113, 114]. 1 H NMR studies have been carried out for the dispersion copolymerization of BMA with PEO macromonomer, 26 (m=7), in a deuterated methanol-water medium [162]. The fractional composition and surface grafted PEO concentration were monitored as the function of conversion and particle size. In Fig. 9, the mobile fraction f M of PEO chains incorporated into the particles is plotted against interchain spacing D as shown in Fig. 8c, which can be calculated using the values of particle size and conversions. One sees that the values of f M increase sharply with decreasing D in the region of D below 1.6 nm and become constant
Poly(macromonomers), Homo- and Copolymerization 173 Fig. 9. Plots of mobile fraction(f M ) of surface anchored PEO chains against the estimated mean separation D between PEO anchor points on the surface of the particles. The D values were calculated from the particle size and number, assuming that all PEO chains were located at the surface below D=1.4 nm. The radius of gyration of the PEO chain coil in methanol is calculated to be 1.6 nm, which corresponds to the D value at which the sharp increase in f M occurs. This result may suggest that the onset of a pancake-to-brush transition of grafted chains at the interface occurs when D» 1/2 , as was expected from theory [130, 154, 155]. This kind of subject is of importance for a better understanding of the true nature of the steric stabilization existing in many dispersion systems. With these guidelines, the macromonomer technique will be used extensively to construct model colloidal systems. 7 Conclusions and Future A number of well-defined macromonomers differing in the types of the monomer and the end functionality have been made available in these two decades. Their polymerization and copolymerization have provided a relatively easy access to a variety of branched polymers and copolymers, including comb-, star-, brush-, and graft-structures. Progress will no doubt continue to disclose further different types of macromonomers and branched polymers. Radical homopolymerization and copolymerization of macromonomers are fairly well understood and reveal their characteristic behaviors that have to be compared with those of conventional monomers. A detailed mechanism of the polymer-polymer reactions involved, however, appears still to be an issue. Ionic or, desirably, living polymerization and copolymerization are still an important
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142 Advances in Polymer Science Edi
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Branched Polymers I Volume Editor:
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Volume Editor Dr. Jacques Roovers I
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Preface While books have been writt
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Contents Synthesis of Branched Poly
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Synthesis of Branched Polymers by C
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72 N. Hadjichristidis, S. Pispas, M
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100 N. Hadjichristidis, S. Pispas,
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Dendrimers and Dendrimer-Polymer Hy
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Author Index Volumes 101-142 Author
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Author IndexVolumes 101-142 231 Dun
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Author Index Volumes 101-142 233 Ka
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Author Index Volumes 101-142 235 Og
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Author Index Volumes 101-142 237 Su
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Subject Index Addition-fragmentatio
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Subject Index 241 Microphases 11z,
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142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

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