Macromolecules
Article
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Table 4. Molecular Weight and Polydispersity of Block
Brush Copolymers
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star
comb
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sPS
sPS-b-PBA
cPS
cPS-b-PBA
Mn
27 600
1.10
107 600
1.16
200 300
1.94
435 400
1.85
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PDI
high-Tg segment in the core and a soft, low-Tg segment in the
shell was confirmed, which is a promising architecture in the
design of thermoplastic elastomeric materials.
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CONCLUSIONS
■
A variety of well-defined, densely grafted molecular brushes
based on polyphosphazenes were synthesized by ATRP poly-
merization. Three different monomersstyrene, tert-butyl
acrylate, and N-isopropylacrylamidehave been grafted from
cyclotriphosphazene or polyphosphazene initiators to form
star- or comb-shaped brush polymers. Both systems follow
first-order reaction kinetics during polymerization, exhibiting
living polymerization features. The resultant polymers show
well-defined structures with controlled molecular weight and
low polydispersity. Also, the side chains, when cleaved from the
skeleton, have a relatively low polydispersity, Mw/Mn ≤ 1.21,
which demonstrates the controlled nature of the grafting
procedure. Positively charged molecular brushes were obtained
through hydrolysis of tert-butyl groups to provide free car-
boxylic acid functional groups. Also, the thermal sensitivity of
poly(N-isopropylacrylamide) brush polymers remains intact
and independent of the side chain length. The interesting
change of hydrodynamic radius before and after its LCST
exhibits the unique properties of single cylindrical brush mole-
cule with stimuli-responsive behavior. Furthermore, the resul-
tant functionalized block brush polymers with a hard poly-
styrene core and a soft poly(tert-butyl acrylate) shell are
promising candidates for a variety of applications in thermo-
plastic elastomeric materials and in the biomedical field, such as
drug delivery and tissue engineering.
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AUTHOR INFORMATION
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