J. Phys. Chem. B 2006, 110, 837-841
837
Study on the Synthesis of Poly(diglycidyl maleate-co-stearyl methacrylate) and Morphology Conversion of Their Self-Assembly Systems Haojie Yu, Li Wang,* Junfeng Zhou, Guohua Jiang, and Zhenrong Zhao State Key Laboratory of Polymer Reaction Engineering, College of Materials Science and Chemical Engineering, Zhejiang UniVersity, Hangzhou 310027, China ReceiVed: September 29, 2005; In Final Form: NoVember 19, 2005
A novel polymer of poly(diglycidyl maleate-co-stearyl methacrylate) (P(DGMA-co-SMA)) was synthesized by reaction between poly(maleic anhydride-co-stearyl methacrylate) (P(MA-co-SMA)) and epichlorohydrin. The self-assembly behavior of the resultant copolymer was investigated. It was found that the spheral aggregates could converse to nanorods after being aged for 2.5 days and nanolines composed of the nanorods were obtained after being aged for an additional 5.5 days. The mechanism of their self-assembly behavior and morphology conversion of self-assembly systems is discussed.
Introduction Self-assembly is a promising way to prepare well-defined nanostructures for drug delivery, microreactors, microcapsules, and encapsulation of various kinds of guest molecules.1-7 Amphiphilic molecules are important optional materials for selfassembly for their unique solution and associative properties.8-10 Various factors that affect the morphologies of amphiphilic molecules, such as molecule composition,11-13 concentration,14 solvents,15 temperature,16 and pH,17 have been widely investigated. A noteworthy phenomenon had been found that morphology conversion occurred in some self-assembly systems. Burke and Eisenberg investigated kinetics and the mechanism of the vesicle-to-rod transition of aggregate systems prepared from the ternary system of polystyrene-b-poly(acrylic acid)/dioxane/ water.18 They also reported morphological conversion in aggregates of polystyrene-b-poly(acrylic acid) induced by the small-molecule surfactant sodium dodecyl sulfate.19 The morphology conversion of aggregates provides a method to prepare some materials with specific shapes. Compounds containing epoxy groups have caught considerable attention for the presence of easily transformable epoxy groups. They have been applied in protein and enzyme immobilization,20,21 biological tissue fixation,22 and biomolecule binding.23 Preparation of amphiphilic molecules containing epoxy pendant chains can provide significant materials used in the fields of nanotechnology, medicine, and biology. Can˜amero et al.24 have synthesized a novel poly(glycidyl methacrylate)b-poly(butyl acrylate) diblock copolymer through atom transfer radical polymerization (ATRP). A self-assembly system with a specific shape and the stability of the resultant micells are required in some applications. Amphiphilic copolymers with epoxy groups have such merits for the epoxy group can cross-link after self-assembly. In this paper, we report a synthesis route of P(DGMA-co-SMA) through grafting the epichlorohydrin to the P(MA-co-SMA) copolymer obtained by ATRP. The resulting copolymer can selfassemble in THF solution, using deionized water as a precipitant. The morphology conversion of the resulting aggregates was * Address correspondence to this author. E-mail:
[email protected]. Phone: +86-571-87953200. Fax: +86-571-87951612.
found and investigated. The mechanism of morphology conversion is discussed. Experimental Section Materials. Maleic anhydride (MA) from Shanghai No. 1 Chemical reagent factory was recrystallized in chloroform before use. Stearyl methacrylate (SMA) obtained from Shanghai No. 1 Chemical reagent factory was washed with 5 wt % of NaOH solution. Di-tert-butyl peroxide (DTBP) purchased from Shanghai No. 1 Chemical reagent factory was treated according to the literature method.25 Epichlorohydrin, an analytical reagent, was used as obtained from Wulian Chemical Plant in Shanghai. Tetrabutylammonium bromide (TBAB) was purchased from Sinopharm Chemical Reagent Ltd. Co. Tetrahydronfuran (THF), NaOH, and CH3CH2OH were purchased from East of China Chem. Ltd. Co. THF was purified by fluxing over a K-Na alloy under nitrogen and other reagents were used as received. Synthesis of P(DGMA-co-SMA). P(MA-co-SMA) was synthesized according to ref 26. 1H NMR (500 MHz, CDCl3): δ 0.88 (3H, in CH3(CH2)15-), 0.86 and 0.90 (3H, in CH3C-), 1.20-1.40 (30H, in -(CH2)15CH3), 1.58-1.78 (2H, in -CH2(CH2)15CH3, 2H, in -CH2C-), 2.2-3.8 (2H, in -CHCH-), 4.13 (2H, in -OCH2-).27 The molecular weight and molecular weight distribution of P(MA-co-SMA) were Mn ) 3371 and PDI (Mw/Mn) ) 1.73. The MA segment content was 15.34 wt %. P(DGMA-co-SMA) was prepared by the reaction of P(MAco-SMA) and epichlorohydrin. The typical synthesis process is as follows: 0.8171 g of P(MA-co-SMA), 4.8 mL of epichlorohydrin, 0.0102 g of TBAB, and 0.15 mL of H2O were mixed in a 25-mL three-necked flask with a magnetic stirrer and a reflux condenser and reacted at 120 °C for 2.5 h. The excessive epichlorohydrin was removed under vacuum after reaction. The product was dissolved in 10 mL of THF at room temperature, after which 0.51 mL of 30 wt % of NaOH solution was added dropwise in 15 min. The reaction was continued for another 2 h. Then the product was purified by precipitation in 200 mL of deionized water 2 times and dehydrated in a vacuum at room temperature. 1H NMR (500 MHz, CDCl3): δ 0.88 (3H, in CH3(CH2)15-), 0.86 and 0.90 (3H, in CH3C-), 1.20-1.40 (30H, in -(CH2)15CH3), 1.58-1.78 (2H, in -CH2(CH2)15CH3, 2H,
10.1021/jp055557l CCC: $33.50 © 2006 American Chemical Society Published on Web 12/21/2005
838 J. Phys. Chem. B, Vol. 110, No. 2, 2006
Yu et al. Results and Discussion
Figure 1. 1H NMR spectrum of P(DGMA-co-SMA).
in -CH2C-), 2.2-3.8 (2H, in -CHCH-), 2.61 and 2.81 (4H, in -CHCH2O-), 3.17-3.27 (2H, in -OCH-), 3.36 and 3.86 (4H, in -OCH2CH
