Conspectus
The phosphorescence is produced
by the radiative transition of
the excited triplet state which is generated by the intersystem crossing
(ISC) from the excited singlet state. Compared with fluorescence,
it has a longer luminescence lifetime and larger Stokes shift, so
phosphorescent materials have great application value in fields such
as displays, anticounterfeiting, and imaging. But due to the low ISC
rate of organic molecules, the slow radiative transition rate of the
triplet state, and the large nonradiative energy loss caused by molecular
vibration, pure organic room temperature phosphorescence (RTP) is
usually difficult to obtain. Among the most widely used strategies
including crystal assembly, polymerization, and host–guest
encapsulation, the polymerization strategy based on rigid polymers
has achieved great success and widespread attention due to their easy
processing and excellent luminescence performance.
The main
function of polymers is to fix the luminophore into the
matrix and suppress the energy loss of the triplet state caused by
nonradiative transitions and oxygen quenching. That is, polymers provide
a rigid microenvironment necessary for the RTP, although some polymers
are flexible and stretchable. Conventional polymers have limited interaction
with luminophores and do not have the function of promoting triplet
states. Therefore, the high RTP quantum yield depends more on the
structural design of luminophores. By modification of the structure,
functionalized polymers can be endowed with the ability to regulate
the singlet and triplet energy levels of luminophores, enhance ISC,
and increase the quantum yield of RTP. The selection of functionalized
polymers also enriches the diverse properties of RTP materials.
This Account summarizes the latest research progress in the field
of polymer-based RTP and RTP enhancement by functionalized polymers.
Luminophores are used to construct RTP systems by doping, covalent
linking, or supramolecular interactions with polymers such as PAA,
PMMA, PVA, and PAM. To further strengthen polymer rigidity, secondary
processing has been successfully employed to synergistically suppress
nonradioactivation and enhance RTP performance, such as hydrogen bonding
bridges, host–guest encapsulation, and cross-linking. The function
of polymers is no longer limited to suppressing nonradiative transitions
but also includes enhancing the yield of triplet states and generating
special luminescence phenomena. A few functionalized polymers are
specially designed to utilize external heavy atom effects, dipole–dipole
interactions, and electrostatic and diffusion interactions with the
luminophores to promote the ISC rate. Due to the diversification and
functionalization of polymers, RTP systems were developed with various
special luminescence phenomena such as photoactivation, excitation
wavelength dependence, photochromism, circularly polarized RTP, and
stimulus-response. We hope the summarized functions and development
trends of polymers in RTP systems can provide helpful gui...