Crosslinked polymeric nanocapsules from polymer brushes grafted silica nanoparticles via surface-initiated atom transfer radical polymerization

doi:10.1016/j.colsurfb.2009.07.042

Colloids and Surfaces B: Biointerfaces

Volume 74, Issue 2, 1 December 2009, Pages 511-515

https://doi.org/10.1016/j.colsurfb.2009.07.042 Get rights and content

Abstract

The crosslinked polymeric nanocapsules with inner diameter of about 20–50 nm were prepared successfully by the post-treatment of the poly(methyl acrylate) (PMA) brushes grafted silica nanoparticles (SN-PMA) produced with the surface-initiated atom transfer radical polymerization (SI-ATRP) technique. The PMA chains grafted were modified with amino groups by being treated with ethanediamine (EDA). Then the silica nanoparticles (SN) templates were removed by being etched with hydrofluoric acid (HF) to produce the crosslinked polymeric nanocapsules after the aminated poly(methyl acrylate) (APMA) chains on the SN templates were crosslinked with hexamethylene diisocyanate (HDI). Transmission electron microscopy (TEM) analyses were used to estimate the size of the polymeric nanocapsules.

Introduction

In recent years, significant progress has been made in the design and fabrication of polymeric microcapsules and nanocapsules, which have attracted great attention because of a variety of applications such as delivery vesicles for drugs [1], [2], [3], [4], catalysis [5], [6], [7], proteins [8], DNA [9], probing single-cell signaling [10], self-healing materials [11] and so on. Large number of physical and chemical routes have been developed for the preparation of polymeric microcapsules and nanocapsules, such as template method [12], [13], [14], [15], [16], layer-by-layer (LbL) assembly [17], [18], [19], micelle formation of block copolymer [20], [21], [22], interfacial polymerization [23], [24], [25], emulsion polymerization [26], [27], [28], [29], and others [30], [31].

In order to assert control over the thicknesses of the shell of the polymeric nanocapsules, strategies based on the surface-initiated controlled/“living” radical polymerization (C/LRP) have been developed with nanoparticles as templates. Microcapsules with a shell of poly(benzyl methacrylate) (PBzMA) brush layer were prepared via SI-ATRP of benzyl methacrylate on silica nanoparticles (about 3 μm) and then etched out the silica templates by treating with hydrofluoric acid (HF). This hollow microsphere can be dissolved into individual free chains in good solvent for PBzMA because there were only van der Waals attractions between the PBzMa brushes [15].

To overcome this drawback, polymeric nanocapsules with a crosslinked shell were produced. PS-b-PMMA block copolymer was grafted to the silica templates via SI-ATRP of styrene and subsequently ATRP of methyl methacrylate (MMA). Then exposure to UV resulted in the crosslinking of the PS shell and the decomposition of the PMMA outer layer. After removal of the SiO₂ core by being etched with HF, hollow nanospheres with crosslinked PS shell of about 20–60 nm in thickness and void cores of about 20–30 nm in diameter were obtained [32].

Furthermore, we previously designed a process to fabricate crosslinked polymeric nanocapsules with inner diameter of about 10–40 nm. These crosslinked polymeric nanocapsules were prepared via the surface-initiated self-condensing vinyl polymerization (SI-SCVP) of p-chloromethyl styrene (CMS) from initiator modified silica nanoparticles with atom transfer radical polymerization (ATRP) technique. The silica templates were removed by etching with HF to produce the crosslinked polymeric nanocapsules after the grafted hyperbranched polymers had been crosslinked [33].

In the present work, we describe a strategy for preparation the crosslinked polymeric nanocapsules with inner diameter of about 20–50 nm based on the template method with widely used sacrificial silica nanoparticles via the surface-initiated atom transfer radical polymerization (SI-ATRP) technique, as illustrated in Scheme 1. Initially the bromoacetamide groups were immobilized onto the surfaces of the silica nanoparticles to initiate the atom transfer radical polymerization of methyl acrylate, then aminated poly(methyl acrylate) (APMA) was crosslinked with hexamethylene diisocyanate (HDI) after the surface side groups (–CO–O–CH₃) had been transformed to amino groups (–CO–NHCH₂CH₂NH₂). Finally, the crosslinked polymeric nanocapsules were obtained after the silica nanoparticle templates had been etched with HF.

Section snippets

Materials and reagents

Silica nanoparticles with average particle size of 10 nm used was MN1P obtained from Zhoushan Mingri Nano-materials Co. Ltd., Zhejiang, China. They were dried in vacuum at 110 °C for 48 h before use.

γ-Aminopropyltriethoxysilane (APTES) (Gaizhou Chemical Industrial Co. Ltd., Liaoning, China) was used as received. Bromoacetylbromide was analytical reagent grade and purchased from Acros Organics (Phillipsburg, NJ, USA). Cu(I)Br (Tianjin Chemical Co., Tianjin, China) was analytical reagent grade and

Results and discussion

The bromoacetamide groups were immobilized onto the surfaces of the silica nanoparticles by the bromoacetylation of the surface amino groups of the aminopropyl-modified silica nanoparticles (AP-SN) with bromoacetylbromide (Scheme 1). After the macroinitiators based on silica nanoparticles (BrA-SN) were washed with anhydrous THF and ethanol thoroughly, the elemental analysis results of C and N indicated that about 3.0 mmol initiating group/g BrA-SN were immobilized. The amide groups

Conclusions

In summary, we developed a strategy for preparing the crosslinked polymeric nanocapsules with inner diameter of about 20–50 nm via the surface-initiated atom transfer radical polymerization (SI-ATRP) technique with silica nanoparticles as templates. The process to prepare the crosslinked polymeric nanocapsules was confirmed by elemental analysis, TGA, FTIR and TEM. It is expected that various crosslinked polymeric nanocapsules could be fabricated via the strategy developed so that the

Acknowledgment

This project was granted financial support from China Postdoctoral Science Foundation (Grant No. 20070420756).

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Crosslinked polymeric nanocapsules from polymer brushes grafted silica nanoparticles via surface-initiated atom transfer radical polymerization

Abstract

Introduction

Section snippets

Materials and reagents

Results and discussion

Conclusions

Acknowledgment

J. Control. Release

Compos. Sci. Technol.

Curr. Opin. Colloid Interface Sci.

J. Am. Chem. Soc.

Angew. Chem. Int. Ed.

J. Nanosci. Nanotechnol.

Nano Lett.

Adv. Funct. Mater.

J. Am. Chem. Soc.

J. Phys. Chem. C

Macromol. Rapid Commun.

Langmuir

J. Am. Chem. Soc.

Adv. Mater.

Adv. Mater.

Chem. Mater.

Langmuir