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Prof. Wu Peiyi's group: a simple and efficient method for preparing polymer nanotubes
2019-12-24 Source: Polymer Technology

Polymer nanotubes have broad application prospects in the fields of biomedicine, catalytic adsorption, metal loading, and nanoreactors due to their narrow hollow structures, large aspect ratios and surface areas. Although the self-assembly of amphiphilic block polymers is an effective method for preparing polymer nanotubes, there are still few studies on its formation mechanism and influencing factors. Recently, Lu Fei , PhD student (Professor Wu Peiyi's research group) at Fudan University, proposed a simple and efficient method for preparing nanotubes through polymerization-induced self-assembly (PISA) using fluorine-containing monomers , and did research on its mechanism and influencing factors. After discussion, related work was published on Macromolecules.

Because of its poor solubility in organic solvents, fluoropolymers have bright performance in PISA. Previously, the research group previously reported the dispersion polymerization of pentafluorostyrene (PFS) and styrene (St) in ethanol to obtain colloidal particles with nucleated blocks of alternating copolymer P (St- alt- PFS). From this, an inverse bicontinuous structure was prepared ( as well as And p6mm hybrid structure) (Nat. Commun. 2019, 10, 1397).

Figure 1. Schematic diagram of the formation of a tubular morphology as the polymerization degree of PPFS increases when the polymerization temperature is less than or close to the solvated glass transition temperature.

)作为亲溶剂嵌段,在乙醇中分散聚合PFS,获得PDMA- b -PPFS胶体颗粒。 Based on this work, we continued to use fluoromonomer PFS as the research object, using poly N, N-dimethylacrylamide (PDMA 29 ) as the solvent-solvent block, and dispersing and polymerizing PFS in ethanol to obtain PDMA- b. -PPFS colloidal particles. By adjusting the degree of PPFS block polymerization and the ratio of co-solvent (DMF), colloidal particles with nanotube morphology were successfully obtained. Through sampling and tracking research in different polymerization stages, it was revealed that the block polymer undergoes the morphological evolution process of spherical-vesicle-nanotubes. However, surprisingly, when the content of the co-solvent DMF was large (20%), they found that the morphological transformation process of the block polymer had changed significantly, undergoing the traditional spherical-worm-like-vesicle- Morphological transformation of compound vesicles.

条件下制备 PDMA 29 - b -PPFS x胶体颗粒的TEM图。 Figure 2. TEM image of PDMA 29 - b -PPFS x colloidal particles prepared at 30% w / v solids in ethanol at 70 ° C.

条件下制备 PDMA 29 - b -PPFS x 胶体颗粒的TEM图。 Figure 3. TEM image of PDMA 29 - b -PPFS x colloidal particles prepared at 70 in 30% w / v solid content, 20% DMF / ethanol .

)的测定,结果表明,随着DMF含量的增加,PDMA- b -PPFS的Tsg逐渐降低。 For this special phenomenon, they used an ultra-sensitive differential scanning calorimeter to measure the solvated glass transition temperature ( T sg ) of block polymers at different DMF contents. The results showed that with the increase of DMF content, The Tsg of PDMA- b- PPFS gradually decreased. )与溶剂化玻璃化转变温度( T sg )的相对关系会对聚合物链的自由度产生较大的影响,他们在分别在乙醇,5% DMF/乙醇,10% DMF/乙醇条件下,通过调节聚合温度(50~80 )与其对应T sg的相对关系,发现当T p大于T sg时,此时PPFS链段自由度较高,因此发生传统的球形-蠕虫-囊泡-复合囊泡的形貌转变;相反,当T p小于或接近于T sg时,PPFS链段自由度受限,此时只能发生囊泡的一维融合,从而发生球形-囊泡-纳米管的形貌演变。 Considering that the relative relationship between the polymerization temperature ( T p ) and the solvated glass transition temperature ( T sg ) will have a greater impact on the degree of freedom of the polymer chain, they are in ethanol, 5% DMF / ethanol, 10% Under DMF / ethanol conditions, by adjusting the relative relationship between the polymerization temperature (50 ~ 80 ° C ) and its corresponding T sg , it was found that when T p is greater than T sg , the degree of freedom of the PPFS segment is higher at this time, so the traditional spherical-worm -Vesicle-complex vesicle morphology transition; on the contrary, when T p is less than or close to T sg , the degree of freedom of the PPFS segment is limited. Morphological Evolution of Bulb-Nanotubes. This work first proposed the use of the relative relationship between the polymerization temperature and the solvated glass transition temperature to regulate the morphological transformation process, which not only deepened the understanding of the nanotube formation mechanism and influencing factors, but also expanded PISA's The preparation range provides an important guarantee for the preparation of subsequent functionalized materials.

PDMA 29 - b -PPFS 180胶体颗粒的溶剂化玻璃化转变温度。 Figure 4. Solvation glass transition temperature of PDMA 29 - b -PPFS 180 colloidal particles in different solvents .

b -PPFS胶体颗粒的形貌转变机理示意图。 Figure 5. Schematic diagram of the morphological transition mechanism of PDMA- b- PPFS colloidal particles under different polymerization temperatures and solvated glass transition temperatures .

This research was supported and supported by the National Natural Science Foundation of China (51733003, 21674059). The first author of the article is Lu Fei , a PhD student in Fudan University, and the corresponding authors are Professor Wu Peiyi and Professor An Zesheng .

Paper link http://pubs.acs.org/doi/10.1021/acs.macromol.9b01868

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