Polymer glasses have an irregular structure. Among
the causes for such complexity are the chemically distinct chain end-groups that
are the most abundant irregularities in any linear polymer. In this work we
demonstrate that chain end induced defects allow polymer glasses to create
confined environments capable of hosting small emissive molecules. Using
environmentally sensitive luminescent complexes we show that the size of these
confinements depends on molecular weight and can dramatically affect the photoluminescence
of free or covalently bound emissive complexes. We confirm the impact of chain
end confinement on the bulk glass transition in poly(methyl acrylate) and show
that commonly observed T<sub>g</sub> changes induced by the chain ends should
have a structural origin. Finally, we demonstrate that size and placement of luminescent
molecular probes in pMA can dramatically affect the probe luminescence and its
temperature dependence suggesting that polymer glass is a highly irregular and
complex environment marking its difference with conventional small molecule
solvents. Considering the ubiquity of luminescent glassy materials, our work
lays down a blueprint for designing them with structural considerations in
mind, ones where packing density and chain end size are key factors.
Environmentally Sensitive Luminescence Reveals Spatial Confinement, Dynamics, and Their Molecular Weight Dependence in a Polymer Glass
