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

Synthesis of Branched Polymers by Cationic Polymerization 59
Dehydrochlorination followed by hydroboration-oxidation resulted in PIB-
CH 2 OH, which was subsequently esterified with methacryloyl chloride.
Scheme 11 helps to visualize the procedure.
The structure and value of F n were determined by 1 H NMR and IR spectroscopies
combined with MW determination by vapor pressure osmometry. According
to the results, MA-PIB macromonomers indeed carried close to one
methacrylate function per molecule. The homopolymerization of a relatively low
MW (M n =5200 g mol –1 ) MA-PIB was attempted by radical means. Polymerization
did not take place in solution. In bulk however, a portion of the macromonomer
polymerized to give a star-like product with high MW (M v ~7.10 5 g mol –1 ).
Free radical nearly ideal copolymerization of MA-PIB with MMA afforded
PMMA-g-PIB copolymers which were optically clear but had disappointingly
low tensile strength and modulus . All graft copolymers exhibited two T gs, one
at ~–65 °C for PIB and one at ~100 °C for the PMMA component, indicating microphase
separated morphology.
Macromonomers with two methacrylate functionalities (MA-PIB-MA) at
both ends of the PIB chain have also been synthesized, by a procedure essentially
identical to that reported above, but starting with a bifunctional initiator
in the polymerization of IB [103]. Free radical copolymerization of the resulting
MA-PIB-MA with 2-(dimethylamino)ethyl methacrylate resulted in
amphiphilic networks, with a wide range of mechanical and swelling properties.
The acrylate or methacrylate functional PIBs have also been used in UVcurable
solventless coatings formulation in the presence of reactive diluents
(multifunctional acrylate or methacrylate esters) and a UV-sensitizer [104].
The products were transparent, flexible films, with very little extractables, in
which hard polyacrylate or polymethacrylate domains were dispersed in the
soft PIB matrix. Tensile strength and ultimate elongation have also been obtained.
The synthesis of MA-PIB macromonomers by three different methods, which
were claimed to be less cumbersome than that above, was reported by Maenz
and Stadermann [105]. The first procedure, as shown in Scheme 12, involved
alkylation of phenol by PIB olefin followed by reaction with methacrylic acid.
The PIB olefins were either commercial products (“Glissopal” by BASF,
“HYVIS 5” by BP Chemical Ltd., and “Polybutene” by Amoco Chemicals Co.)
or were obtained by selective polymerization of butadiene free C 4 -fractions. It
should be noted that before esterification non-functional PIBs, present in the
commercial products in varying amounts, were removed by column chromatography.
The best results were obtained with Glissopal which had the highest
double bond functionality, ~0.85. Interestingly, the number average double
bonds (F n(DB)) determined by ozonolysis or by 1 H NMR spectroscopy differed
considerably and relatively good correlation between F n(DB) and F n of PIBphenol
was obtained only for Glissopal. This suggests that in the other samples
a relatively large fraction of the double bonds were not located at the polymer
end. The second synthetic route is shown in Scheme 13.