The stability of self-assembled nanofibers controlled by supramolecular copolymerization

Introducing the concept of supramolecular self-assembly into traditional polymers can not only improve the properties of polymers, but also expand the application of polymers in the field of functional materials In the past 20 years, scholars have studied the polymerization mechanism of supramolecular polymer in detail, and developed a series of polymer materials with higher performance through new driving force In addition, on the basis of the study of polymer properties, the researchers realized the regulation of polymer microstructure by controlling the process of supramolecular copolymerization However, the polymer prepared by supramolecular interaction has been faced with a huge problem - how to accurately control the stability of the polymer? The traditional polymer is formed by the combination of monomers through covalent bond, so in the process of copolymerization, the properties of the polymer can be precisely controlled by adjusting the activity of different monomers However, in the preparation of supramolecular polymers, the conversion between monomers and polymers is a dynamic equilibrium process How to control this equilibrium process and increase the stability of polymer is always a research difficulty Fig 1 The structure of supramolecular polymer monomer (photo source: angelw Chem Int ed.) recently, Professor Anja R A palmans and Professor E W Meijer from Eindhoven University of technology in the Netherlands jointly reported the supramolecular copolymerization based on two 1,3,5-benzenetriamide type molecules (NBTA and DBTA, Fig 1) As the copolymerization of maleic anhydride and styrene, DBTA alone can not be polymerized; if NBTA is added to the system, the two can be polymerized The formation process and stability of supramolecular polymers were characterized by cryoTEM and hdx-ms it was found that when the NBTA content in the system is high, they tend to form spherical polymers, while when the ratio of the two is similar, they will form stable fibrous polymers This achievement was published in German Applied Chemistry (DOI: 10.1002 / anie 201802238) under the title of "supramolecular copolymerization as a strategy to control the stability of self ‐ assembled nanofibers" Fig 2 UV, IR and frozen electron micrograph of the polymer (photo source: angel Chem Int ed.) firstly, the polymerization of NBTA and DBTA was characterized by UV visible absorption spectroscopy (UV / VIS), Fourier transform infrared spectroscopy (FTIR) and cryo TEM (Fig 2) The results show that the content of NBTA in the reaction system has a great influence on the spectral properties and morphology of the copolymers When the content of NBTA is less than 50%, the copolymers are fibrous, and their UV absorption spectra are different from those of DBTA and NBTA However, when the content of NBTA is more than 50%, spherical copolymers appear, and their UV absorption spectra are very similar to those of NBTA By comparing db1bta (containing one dendrite) and d2bta (containing two dendrites) with NBTA, the author speculated that the spectral properties and morphology of the copolymer were related to the number of dendrimers on DBTA Fig 3 After hydrogen deuterium exchange test (picture source: angelw Chem Int ed.), the stability of the copolymer was characterized by hydrogen deuterium exchange test (Fig 3) After exchange, there are two deuterium products in NBTA: one is nbta3d, which has only protons on the hydroxyl group replaced by deuterium, and the other is nbta6d, which has protons on both the hydroxyl group and the amino group replaced by deuterium After exchange, DBTA has only one product, dbta15d It is found that dbta12d, a deuterized product with only the protons on the hydroxyl group, will appear if NBTA is added to DBTA This shows that some amino groups on DBTA are "protected" after the formation of copolymer In addition, by comparing the content of nbta3d in NBTA: DBTA = 1:1 copolymer and DBTA alone, the author found that nbta3d had more content in the former This shows that compared with the single component polymer, the exposed amino group in the copolymer is less, which indirectly shows that the stability of the monomer is improved after the formation of the copolymer In addition, the molecular dynamics simulation of NBTA: DBTA = 2:1 shows that the order degree of monomers in the supramolecular polymer increases with the addition of DBTA Finally, the author indicated that the properties similar to those of styrene maleic anhydride copolymer showed the commonality between macromolecular and supramolecular polymer Full text author: balan S thota Xiangwen Lou David E bochicchio Tim F E paffen Ren é p m lafleurjoost L J van Dongen Svenja Ehrmann Rainer Haag Giovanni M pavan Anja R A palmans E W Meijer