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Blair Brettmann, Marco A. Fraga, Monika Gosecka and Natalie Stingelin introduce the cross journal themed collection on Polymer Upcycling.

We have shown that clotrimazole formulations encapsulated in polyether-based unimolecular micelles have significantly higher antitumour activity than the drug itself.

Polyester polyols synthesized via a polycondensation reaction of diols with diacids or their diesters are commonly used as polyurethane building blocks. Herein, we demonstrate an alternative route to polyester polyols via oxidative esterification of aliphatic α,ω-diols. Unlike the polycondensation reaction, this process is carried out in aqueous media at 30 °C under atmospheric pressure. In situ generated hypobromous acid from the mixture of NaBr, NaBrO3 and H2SO4 is used to trigger the reaction. The reaction progress can be conveniently controlled with the Br/OH molar ratio. The properties of the obtained polyesters are determined by the applied diol and can be tailored using a mixture of diols. The composition of polymers is determined with GPC, NMR, and MALDI-TOF MS. It is shown that polyesters obtained with this method can be used as precursors for polyurethane synthesis. This work provides a quick and convenient route to polyester polyol synthesis, feasible in any laboratory.

In this study, we report the synthesis and phase behaviour of statistical p(N-isopropylacrylamide-co-2-acrylamidephenylboronic acid) P(NIPAM-co-2-AAPBA) copolymers. They were obtained via free radical copolymerization of NIPAM and the pinacol ester of 2-acrylamidephenylboronic acid. The influence of copolymer composition on the demixing/mixing temperature was investigated by means of UV/Vis spectrometry, DLS, DSC, and 1H NMR spectroscopy. The turbidity experiments revealed the gradual increase of the cloud point with the increase of 2-AAPBA content in the copolymer up to 37 °C at 30 mol%. The copolymer with 45 mol% did not display any transition. For copolymers displaying the cloud point, the hysteresis in the demixing/mixing temperature was observed. Transmittance measurements, DLS, and 1H NMR spectroscopy demonstrated that the phase transition was sharp upon heating, whereas the phase transition of the copolymer upon a decrease of temperature occurred in a much wider temperature range. Moreover, the NIPAM copolymer with 5 mol% 2-AAPBA content displayed 5 °C hysteresis, whereas for the copolymer containing 30 mol% 2-AAPBA it reached 25 °C. Actually, nanoparticles were formed from the copolymer with 30 mol% of 2-AAPBA above the cloud point, which were stable upon cooling to 5 °C showing the potential for drug delivery applications. Raman spectroscopy applied for the analysis of an aqueous solution of NIPAM copolymer with 15 mol% content heated over the cloud point revealed the appearance of a vibrational band at 753 cm−1 characteristic of boroxine, i.e., boronic acid anhydride, the formation of which explains the broadening of the hysteresis. The detailed analysis of experimental data supported with DFT calculations evidenced the presence of other vibrational bands of 2-AAPBA anhydride (780, 957 and 999 cm−1). This is the first report of boroxine formation upon the phase transition of boronic acid-based thermoresponsive copolymers.

Selective homodimerization of glycoluril molecular clips makes this class of molecules valuable supramolecular motifs with great potential in the area of reversibly cross-linked self-healable polymer materials. However, their introduction into a polymer matrix requires suitable functionalization on the clip convex site, which does not participate in the association processes. Generally, the glycoluril clip's convex site is equipped with two ester groups, 1. The presence of two functional groups is usually undesired during the polymerization process or any functionalization reactions. A monofunctionalized glycoluril clip would assure targeted and convenient clip introduction into a polymer structure. Here, we present the successful synthesis of a glycoluril clip with a monohydroxylated convex face, 3, which was easily obtained from the dihydroxyl clip derivative, 2, under mild conditions, in the cyclization reaction of diethanolamide groups into an N-(2-hydroxyethyl) five-membered imide, applying a catalytic amount of weak organic acids. Experimental data supported by computer simulation facilitated determination of optimal conditions of a new clip formation. Moreover, we demonstrated a possibility of a direct conversion of a diester clip, 1, into a clip, 3, eliminating one reaction step. The structure of the glycoluril clip 3 was confirmed using ESI-MS, and 1D and 2D NMR spectroscopy. DFT calculations carried out for clips equipped with diester, diethanolamide and monohydroxylated cyclic imide groups, respectively, revealed that upon the clip's convex functionalization, including cyclization, the size of the clip's cleft does not change, which is of great importance in view of the clip association ability. Variable-temperature 1H NMR spectroscopy in the range from 223 to 323 K confirmed the ability of the new clip to dimerize, demonstrating its thermosensitive character. In addition, the clip exhibits high thermal stability up to 453 K, which is crucial in view of the synthesis and processing of clip-based polymer materials.