Multicomponent Spiropolymerization of Diisocyanides, Diethyl Acetylenedicarboxylate, and Halogenated Quinones

Access to 2,4-Disubstituted Pyrrole-Based Polymer with Long-Wavelength and Stimuli-Responsive Properties via Copper-Catalyzed [3+2] Polycycloaddition

Pyrrole-based polymers (PBPs), a type of fascinating functional polymers, play a crucial role in materials science. However, efficient synthetic strategies of PBPs with diverse structures are mainly focused on conjugated polypyrroles and still remain challenging. Herein, an atom and step economy protocol is described to access various 2,4-disubstituted PBPs by in situ formation of pyrrole core structure via copper-catalyzed [3+2] polycycloaddition of dialkynones and diisocyanoacetates. A series of PBPs is prepared with high molecular weight (Mw up to 18 200 Da) and moderate to good yield (up to 87%), which possesses a fluorescent emission located in the green to yellow light region. Blending the PBPs with polyvinyl alcohol, the stretchable composite films exhibit a significant strengthening of the mechanical properties (tensile stress up to 59 MPa, elongation at break >400%) and an unprecedented stress-responsive luminescence enhancement that over fourfold fluorescent emission intensity is maintained upon stretching up to 100%. On the basis of computational studies, the unique photophysical and mechanical properties are attributed to the substitution of carbonyl chromophores on the pyrrole unit.

Recent progress on polymerization-induced emission

The aggregate luminescence behaviors of polymeric luminescent materials have been attracting great attention. However, the importance of the polymerization process on luminescence, namely, polymerization-induced emission (PIE), has rarely been overviewed. In this review, recent advances in polymerization with PIE effects are summarized, including PIE with aromatic rings based on one-/two-/multi-component polymerizations, and PIE without aromatic rings according to disparate mechanisms of polymerizations. Typical examples are selected to elaborate the basic design principles, as well as the properties and potential applications of the luminous polymers. Moreover, the challenges and perspectives in this area are also discussed.

Regulation of hydrogen bonding network between cellulose nanofibers by rare earth ion Y3

Cellulose is regarded as the most abundant biomass, and nanocellulose derived from it has numerous applications in environmentally friendly materials. However, owing to the abundant hydroxyl groups on surface, nanocellulose is prone to agglomeration when transported, stored, or made into materials, which destroys material performance and limits its use. In this study, a feasible method was presented for regulating the hydrogen bonding strength between cellulose nanofibers (CNFs) by adding a minute quantity of rare earth ions Y³⁺ during cellulose nanofibrillation. It was found that the strength of hydrogen bonding between CNFs can be regulated by controlling the quantity of Y³⁺ in the system. The dispersibility and stability of CNFs, as well as the mechanical properties of CNFs films and CNFs-reinforced papers can be improved by 43.07 % and by 64.05 % after adding only 0.05 or 0.075 wt% Y³⁺. The possible mechanism of CNFs hydrogen bonding network reconstruction was proposed.

Clusterization-Triggered Color-Tunable Room-Temperature Phosphorescence from 1,4-Dihydropyridine-Based Polymers

A series of poly(1,4-dihydropyridine)s (PDHPs) were successfully synthesized via one-pot metal-free multicomponent polymerization of diacetylenic esters, benzaldehyde, and aniline derivatives. These PDHPs without traditional luminescent units were endowed with tunable triplet energy levels by through-space conjugation from the formation of different cluster sizes. The large and compact clusters can effectively extend the phosphorescence wavelength. The triplet excitons can be stabilized by using benzophenone as a rigid matrix to achieve room-temperature phosphorescence. The nonconjugated polymeric clusters can show a phosphorescence emission up to 645 nm. A combination of static and dynamic laser light scattering was conducted for insight into the structural information on formed clusters in the host matrix melt. Moreover, both the fluorescence and phosphorescence emission can be easily tuned by the variation of the excitation wavelength, the concentration, and the molecular weight of the guest polymers. This work provides a unique insight for designing polymeric host-guest systems and a new strategy for the development of long wavelength phosphorescence materials.

In Situ Generation of Heterocyclic Polymers by Triple-Bond Based Polymerizations

Stemming from unique ring structures, heterocyclic polymers exhibit distinguished electrical, mechanical, and photophysical properties and have been widely used in a variety of important applications. Along with the technological significance are the challenges in their synthesis. Traditional synthetic strategies toward heterocyclic polymers often require the direct attachment of heterocycles to polymer backbones, which are generally limited by the lack of suitable and low-cost heterocyclic monomers, tedious reaction process, difficulties in incorporation of multiple substitutents, etc. Alternatively, in situ construction of heterocyclic polymers via triple-bond based polymerization offers promising prospects. This review summarized the recent progress on polymerizations of triple-bond based monomers including alkynes, nitriles, and isonitriles that can in situ generate heterocyclic polymers. The properties and advanced applications of the derived heterocyclic polymers will also be discussed. Finally, the future perspectives and challenges in this field will be addressed.