A triblock PEG-based polymer (CP1113) with a clear ABA structure was synthesized from 1,13-tridecanedioic acid (DA13) and mono-methoxy-poly(ethylene glycol) (MePEG) via condensation reaction. An inclusion complex (IC1113) with β-cyclodextrin (CD) was prepared by co-precipitation and the IC formation was confirmed by transmittance determination with a UV-Vis spectrometer. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetry analysis (TGA) were adopted to characterize IC1113 and the experimental data showed that a channel-type polypseudorotaxane was formed. For further investigating the inclusion behaviors, 1H-NMR spectroscopy was used to determine the molar ratio between CP1113 and β-CD and 2D ROSEY spectra were recorded to elucidate the IC formation mechanism. The results revealed that β-CD threaded onto the polymer main chain at a molar ratio of 7.8 : 1 and the molar ratio of EG segments to β-CD in IC1113 was ca. 8.28 : 1. It was concluded that β-CD accommodated both the methylene and the PEG segments and herein hydrophobic and hydrogen-bonds interactions played the most important roles with a hydrophobic stabilizing and hydrogen-bond inducing effect, which “amplified” the hydrophobic interaction between β-CD and the methylene segment along the hydrophilic PEG segments.
RAFT-mediated polymerization-induced self-assembly (RAFT-PISA) has been undergoing fast development currently, promoting research toward more diverse morphologies and more cutting-edge applications. Herein, we demonstrate a polymerization-pH tailored RAFT-PISA (pH-PISA) process, which can conveniently harvest abundant nano/micro-scale morphologies using popular monomers N,N-dimethylacrylamide (DMAA) and diacetone acrylamide (DAAM). The process proceeded through ordinary RAFT dispersion polymerization in an aqueous medium but under different pH conditions. With the use of pH-sensitive bi-carboxylic acid-capped trithiocarbonate as the chain transfer agent (CTA), it was found that the PISA of propagating amphiphilic ABA triblock copolymers was highly affected by the different ionization of the CTA. When the polymerization pH was adjusted to 2.5, an especially wide spectrum of morphologies was detected, including spheres, worms, lamellae, single or double-head tadpoles, vesicle strings and large spheres with surface protrusions. However, the diversity in morphology gradually declined when the polymerization pH was increased to 6 or 8. Diverse structures with same monomer compositions provide an ideal model to explore the influence of particle morphology on ice recrystallization inhibition (IRI) activities. The variations in mean largest grain sizes (MLGS) and growth rates of a single ice crystal were related to packing parameters (P), bridging the interface geometry of the packing of amphiphilic molecules and ice-controlling activities.
Although triblock polycarbonate thermoplastic elastomers (TPEs) have recently attracted great interests due to their biodegradability, insufficient attentions have been paid to improving the elastomeric properties. Through a tandem reaction strategy involving CO 2 / allyl glycidyl ether (AGE) / cyclohexene oxide (CHO), poly(cyclohexene carbonate)-b-poly(allyl glycidyl ether carbonate)-b-poly(cyclohexene carbonate) (PCAC) is successfully synthesized using a metal-free Lewis acid-base pair catalyst. The synthesized PCACs are pure well-defined ABA triblock all-polycarbonate, which is supported by 1 H NMR, gel permeation chromatography (GPC), and diffusion-ordered spectroscopy (DOSY). A simple modification by grafting alkylthiol chains to PCAC results in excellent TPEs named PCAC-g-S-C a H 2a+1 (PCASaC). The synthesized TPEs are characterized by atomic force microscopy (AFM), thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and mechanical test. They demonstrate a semi-network and semi-domain phase separation structure, wide service temperature range, good strength, high elongation, and extremely high elastic recovery properties. This low-cost, biodegradable, high-performance TPE shows great potential for applications in biomedical, wearable products, sports equipment, and other fields.
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