The monomer
9-[(tert-butyldimethylsilyl)oxy][2.2]paracyclophan-1-ene
(1) is polymerized by Mo(NAr)(CHCMe2Ph)(OCMe(CF3)2)2
(Ar = 2,6-diisopropylphenyl) in a living manner. Block
copolymers containing poly(1)
and polynorbornene (poly(NBE)) can be prepared and have narrow
polydispersities. Treatment of poly(1)
with
NBu4F produces
poly(9-hydroxy[2.2]paracyclophan-1-ene) which
dehydrates to poly(p-phenylenevinylene)
(PPV)
under mild conditions. Block copolymers containing segments of
size-specific and defect-free PPV with poly(NBE)
of various dimensions can be prepared readily and are soluble in a
variety of common organic solvents. These
polymers serve as excellent candidates to measure the effect of chain
length and frequency of interchain contacts on
PPV's fluorescence quantum yield (Φf). Solution and
solid-state quantum yield determinations, coupled to
fluorescence
lifetime measurements, reveal an acute drop in Φf as the
degree of polymerization of the emissive species increases
and as the average distance between PPV chains decreases.
PPV
x
-block-poly(NBE)
y
prepared in solution consistently
shows larger Φf than material prepared by solid-state
dehydration. The poly(NBE) companion block also serves
to
protect PPV from atmospheric degradation.
A series of bis(vinylthienyl)silane monomers were
prepared by reaction of 2 equiv of
(vinylthienyl)lithium or (vinylthienyl)magnesium bromide with
different dichlorosilicon dialkyls. The
monomers react with the Schrock initiator
Mo(NAr)(CHCMe2Ph)(OCMe(CF3)2)2
(Ar = 2,6-diisopropylphenyl), via the acyclic diene metathesis polymerization (ADMET)
mechanism, to give poly(silanyl−dithienylethene) derivatives in excellent yield. GPC data suggest
that the resulting polymers have short
repeat sequences. Interchromophore cooperativity is evident, as a
low energy emission, for polymer
structures that have smaller side groups. This phenomenon is
similar to the chromophore cooperativity
observed in polymers containing stilbene fragments along the
backbone.
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