H-Bonding vs Non-H-Bonding in 100% Pyrene Methacrylate Comb Polymers: Self-Assembly Probed by Time-Resolved Emission Spectra and Temperature Dependent Fluorescence

Abstract

The differences in self-organization behavior in novel 100% pyrene labeled comb methacrylate polymers probed as a function of their varied origins of excimer formation are presented. The different structural variations in the polymers included the presence or absence of hydrogen bonding interactions in the form of urethane linkages, short or long alkyl spacer segments separating the pyrene units from the polymer backbone and linear versus kinked urethane linkage. The effect of variable concentration and temperature on the chemical shift of the NH proton of the urethane linkage was probed using (1)H NMR experiments conducted at temperatures varying from 25 to 70 °C at two different concentrations (2.5 and 25 mmol) in DMSO-d6 as solvent. The photophysical properties of the polymers in dilute DMF solutions were investigated by steady state emission, fluorescence decay studies, time-resolved emission spectra (TRES), and variable temperature emission studies. It was observed that the polymer poly(PBH) having a non-hydrogen-bondable ester linkage in the pendant chains formed an excimer completely via a static mechanism and the ground state aggregate species were not broken even at higher temperatures. The polymer poly(PIC) having a short hydrogen-bondable urethane linkage formed an excimer via a static as well as dynamic mechanism. The other hydrogen-bondable urethane methacrylate polymers having a linear linker poly(PHH) and kinked linker (PIHP) formed excimer mostly via a dynamic mechanism with a very small contribution from the static route. The TRES studies carried out for the polymers provided significant insight into the excimer formation mechanism in these polymers. The variable temperature fluorescence studies highlighted the differences in the H-bonded vs non-H-bonded polymer as a function of their excimer recovery upon cooling.

Photophysics of Pyrenyl-Functionalized Poly(isobutylene-alt-maleic anhydride) and Poly(isobutylene-alt-maleic N-alkylimide). Influence of Solvent, Degree of Substitution, and Temperature

“…The decay constants attributed to the loss of excimers (τ E2 ) were ca. 80–98 ns, values similar to those of poly­(acrylic acid) randomly labeled with pyrenyl groups in methanol (∼77 ns) and THF (∼96 ns). , …”

“…445 nm. These and the fluorescence decay data indicate that only two species are emitting within the 20 ns time window explored and that one (the monomer) “feeds” into the other (the excimer) . Although a part of the excimer emission from 50%Py-PIMA can be attributed to ground-state associated pyrenyl units, another arises from postexcitation associations.…”

“…Thus, end-to-end encounters, leading to excimer formation, could be described by a small number of rate constants. , Later studies have investigated the photophysical properties of pyrenyl end-labeled polydisperse polymers or randomly labeled polymers. In large part, our increased understanding of the much more complex dynamic decays of the emissions can be attributed to models developed by the group of Duhamel during the past two decades. ,,− Among other observations, they found that the fluorescence response is extremely sensitive to the nature of the linker connecting the pyrenyl group to the polymer backbone. , Also, it is known that polymers with large degrees of pyrenyl substitution give rise to a variety of emitting species, including monomers, excimers from ground-state aggregates, and dynamically formed excimers in relaxed or “strained” orientations. , Here, 1-(aminomethyl)­pyrene groups have been attached covalently and randomly as N- imides to PIMA in degrees of substitution ranging from ca. 1% to >90%.…”

pH Dependent Self‐Assembly of Single‐Pyrene‐Armed Calix[4]arene: Modulation and Complexation with p‐Sulfonatocalix[6]arene

“…This long lifetime component is in very good agreement with the lifetime value reported by Costa T for ground‐state pyrene aggregates . Further, we do not observe any growth component in the transient decay traces (usually characterized by a negative pre‐exponential factor) which further supports our conclusion derived from steady‐state emission measurements, that the emission at 450 nm originates from dimer or ground‐state aggregates and not from pyrene excimer. However, upon addition of SCX6 (6.12 mM), the transient decay traces become faster and an additional decay component of 1.09 ns (42.4%) is required to satisfactorily fit the data whereas the amplitude of 3.5 ns component, corresponding to dimers, significantly decreases from 99% to 54% (Table 1).…”

Ionoprinting controlled information storage of fluorescent hydrogel for hierarchical and multi-dimensional decryption

“…The fluorescent monomer (PyMA) was first synthesized through the condensation reaction between HEMA and 1-pyrenylbutyric acid according to previous work (Figs S1, S2) [26]. As depicted in Scheme 1e, the hydrogel was prepared by copolymerizing fluorescent monomer (PyMA) with pH-responsive monomer (AAc) and neutral monomer (AAm) using free radical polymerization in the presence of BIS (crosslinker), APS (initiator) and TEMED (accelerator).…”