Surface Encapsulation Of Nanoparticles With Polycyclopentene Via In Situ Induced Crystallization Process

Surface modification of nanoparticles with polymers is of great importance for their successful applications in various fields as it can introduce specific functionalities onto the surface of nanoparticles. Anew strategy, herein, is successfully explored for the encapsulation of nanoparticles with polymers. A series of polycyclopentene (PCP)-encapsulated nanoparticles were synthesized via in situ polymerization of cyclopentene under mild conditions with a late transition metal catalyst, Pd-diimine, in the presence of nanoparticles (Fe3O4nanoparticles or multi-walled carbon nanotubes (MWCNTs), based on an in situ induced crystallization mechanism. Influence of various process factors on above in situ induced crystallization course were systematically investigated based on structual characterizations of the as-synthesized composite nanoparticles.(1) Oleic acid-modified magetic Fe3O4nanoparticles were first synthesized via a coprecipitation process and then in situ polymerizations of cyclopentene were performed at35℃with an acetonitrile Pd-diimine catalyst (1) in the presence of the as-synthesized Fe3O4nanoparticles to render a series of PCP-encapsulated magnetic nanoparticles based on in situ induced crystallization mechanism. The encapsulation of Fe3O4nanoparticles with PCP was well testified via structural characterizations with thermogravimetry analysis (TGA), Fourier-transformed infrare spectra (FT-IR), wide-angle X-ray diffraction (WAXRD), transmittance electron microscopy (TEM) and scanning electron microscopy (SEM). Influence of various factors including polymerization temperature, time and surface status of nanoparticles were examined and it is indicated that the encapsulation ratio of PCP on nanoparticles can be effectively adjusted via changing polymerization time. The oleic acid-modified Fe3O4nanoparticles are easier to be encapsulated by PCP as compared to the pristine Fe3O4nanoparticles. It is also found that the PCP-encapsulated Fe3O4nanoparticles exhibit well-remained magnetic performance.(2) A Pd-diimine catalyst (2) functionalized with an isobutyryl bromide group capable of initiating atom transfer radical polymerization was synthesized following literature procedures. Then in situ polymerizations of cyclopentene with the as-synthesized catalyst2were performed at35℃in the presence of MWCNTs, giving a series of PCP-encapsulated MWCNTs bearing isobutyryl bromide group based on the in situ induced crystallization mechanism. It is testified, based on various characterization results from TGA, TEM, SEM, WAXRD, differential scanning calorimetry (DSC), FT-IR analysis, that PCP has been homogeneously coated onto the surface of MWCNTs to form a nanowire-like PCP-encapsulated MWCNTs composite. It is also demonstrated that the PCP layer thickness and encapsulating ratio could be effectively adjusted via changing polymerization temperature, catalyst concentration and feed ratio of MWCNTs. Also, the synthesized PCP-encapsulated MWCNTs is found to have stable encapsulating structure with improved dispersibility in THF as compared to the pristine MWCNTs.(3) The as-synthesized PCP-encapsulated MWCNTs was further used as macroinitiator to initiate the ATRP of MMA and PMMA-grafted PCP-encapsulated MWCNTs were successfully achieved. TGA, TEM, FT-IR and DSC analysis confirms the presence of grafted PMMA onto MWCNTs surface and it is found that the grafting ratio of PMMA can be adjusted via changing polymerization time.