A family of cyano-bridged perovskite-like coordination polymers (CPs), [(CH3)nNH(4-n)]2[KFe(CN)6] (n = 1 (1), 2 (2), 3 (3), and 4 (4)), were synthesized and characterized. The differential scanning calorimetry measurements and variable-temperature single-crystal X-ray structural analyses revealed that, owing to the deformation of the host framework as well as the dynamic transition of the guest cation between the static/ordered and dynamic/disordered states, the four CPs undergo structural phase transitions (at 429, 226, 316, and 350 K, respectively) with the symmetry breakings dependent on the symmetries of the encapsulated guest cations. The modulated differential scanning calorimetry measurement suggested that the phase transitions of 1 and 3 have more striking kinetic processes related to their drastic deformation of the host framework as well as a very significant alteration of the host-guest interaction during the phase transition. Moreover, accompanying the transitions between low- and high-temperature phases, the step-like transitions between low and high dielectric states were observed in 1-3, and the corresponding change in amplitude of the dielectric constant is dependent on the total dipole moment of each cage in the high-temperature phase. The investigation on these host-guest CPs deepens the understanding of the relationship between the dipole moment of guest cations and the dielectric behaviour of materials, shedding light on the search for new switchable molecular dielectrics.

Molecular bottlebrushes featuring brush-on-brush (BoB) architecture were prepared by combining azide–alkyne click chemistry, ring-opening polymerization (ROP), and atom transfer radical polymerization (ATRP). Primary side chains of diblock copolymers with a poly­(ε-caprolactone) (PCL) block and a poly­(α-bromo-ε-caprolactone) (P­(CL-Br)) block were synthesized by ROP and then grafted onto PCL backbone by the click reaction. Then the secondary side chains of poly­(oligo­(ethylene glycol) acrylate) (POEGA) were grafted from the P­(CL-Br) block by ATRP, yielding an amphiphilic core/shell structure. Imaging of individual macromolecules by atomic force microscopy (AFM) demonstrated dramatically thickened wormlike formation with distinct hairy side chains. Interestingly, for the BoB molecular bottlebrushes with enough long primary and secondary side chains, sufficient tension can be generated along the backbone and thus lead to its cleavage.

This article demonstrates the synthesis of a new kind of cationic poly­(δ-valerolactone) with primary amino groups at α-positions (poly­(α-NH2-VL)) via ring-opening polymerization (ROP) of α-NHBoc-valerolactone (α-NHB-VL) followed by a simple deprotection reaction. The ROP of α-NHB-VL using benzyl alcohol as an initiator and DBU/TU (1,8-diazabicyclo[5.4.0]­undec-7-ene/thiourea) as a catalytic system in THF at room temperature afforded poly­(α-NHB-VL) with narrow molecular weight distribution. The 1H NMR and MALDI-TOF MS analysis of poly­(α-NHB-VL) indicated that each polymeric chain was capped by the initiator. Kinetic experiments confirmed the living nature of the DBU/TU-catalyzed ROP of α-NHB-VL in THF. The copolymerization result indicated that the polymerization activity of α-NHB-VL is comparable to that of ε-caprolactone (CL) and VL. In addition, block copolymers containing poly­(α-NHB-VL) were successfully synthesized regardless of whether hydrophilic PEG or hydrophobic PCL was used as the macroinitiator. Moreover, water-soluble poly­(α-NH2-VL) was obtained by treatment with trifluoroacetic acid (TFA). It was found that poly­(α-NH2-VL) degraded more slowly at pH 5.5 than at pH 7.4 through a hydrolysis kinetics study.

A desirable triple-shape memory effect showing stable yet easily tunable temporary shapes is achieved using a physically crosslinked network with photo-responsive coumarin-containing poly(ε-caprolactone) as soft segments and poly(l-lactide) as hard segments.

Mechanochromic mechanophores have promising applications in stress sensing and damage detection. Here we report a simple mechanofluorochromic mechanophore based on aminothiomaleimide (ATM). Poly­(methyl acrylate) containing this mechanophore (ATM-PMA) was synthesized by atom transfer radical polymerization (ATRP) using an ATM-derived difunctional initiator. To investigate its mechanofluorochromism, the solution of ATM-PMA was subjected to ultrasonication, and size exclusion chromatography (SEC) and fluorescence spectroscopy were employed to monitor the changes in molecular weight and fluorescence emission. The results showed that the molecular weight of ATM-PMA decreased upon ultrasonication, accompanied by a shift of fluorescence emission from bright yellow to light blue. This mechanophore of a simple functional group of ATM has great potential to be used in mechanochromic polymer materials.