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Download fileEnvironmentally Sensitive Luminescence Reveals Spatial Confinement, Dynamics, and Their Molecular Weight Dependence in a Polymer Glass
journal contribution
posted on 02.09.2021, 19:08 authored by Stephen
J. Picken, Georgy A. FilonenkoPolymer 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) (pMA) and show
that commonly observed Tg changes induced
by the chain ends should have a structural origin. Finally, we demonstrate
that the 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.
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luminescent glassy materialsluminescent molecular probeschain end confinementbulk glass transitionmolecular weight dependencechain end sizeg </ submolecular weightchain endstemperature dependencepolymer glass>< substructural originstructural considerationsprobe luminescencepacking densitylinear polymerkey factorsirregular structurehighly irregulardramatically affectconfinements dependscomplex environmentcommonly observedchanges inducedabundant irregularities