{'fraction_non_alphanumeric': 0.04080351537978657, 'fraction_numerical': 0.0018832391713747645, 'mean_word_length': 5.250980392156863, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
An enzyme-catalysed access to amphiphilic triblock copolymer of PCL-b-PEG-b-PCL: synthesis, characterization and self-assembly properties

Biodegradable amphiphilic triblock copolymer of PCL-b-PEG-b-PCL was synthesized by a simple, environmentally friendly and one-pot biocatalytic route that employs lipase Novozym-435 as a biocatalyst and poly (ethylene glycol) (PEG) as a macromolecular initiator to induce ring-opening polymerization of ε-caprolactone (ε-CL). The structure of the prepared copolymers was characterized by gel permeation chromatography, Fourier transform infrared spectrum and nuclear magnetic resonance spectrum. The crystalline behaviours of the PCL-b-PEG-b-PCL were investigated by differential scanning calorimetry and X-ray diffraction. The self-assembly behaviours of the amphiphilic PCL-b-PEG-b-PCL were studied by fluorescence technique, dynamic light scattering instrument and transmission electron microscopy. The structure analyses indicate that PCL-b-PEG-b-PCL with desired components can be synthesized by changing the molar ratio of ε-CL monomer and PEG macroinitiator. Interestingly, the crystalline structure of PCL-b-PEG-b-PCL is mainly determined by the crystallization of PCL block, suggesting that the crystallization of PEG block in the copolymer is inhibited by the PCL block. The self-assembly behaviours of PCL-b-PEG-b-PCL in water can be adjustable according to the molar ratio of ε-CL and PEG. Size of the formed PCL-b-PEG-b-PCL micelles increased and the critical micelle concentration decreased while the polycaprolactone chain length increased.