Precise Tuning of Micelle, Core, and Shell Size by the Composition of Amphiphilic Block Copolymers Derived from ROMP Investigated by DLS and SAXS

Abstract

Self-assembly of well-defined block copolymers in solution has gained attention not only for its scientific value but also for its potential application in nanotechnology. In this study, we present a comprehensive series of synthesized block copolymers that allows conclusions to be drawn how to design micelles by ROMP with defined core−shell geometry and controlled size. We used a general route for the preparation of well-defined block copolymers by ring opening metathesis polymerization (ROMP) with “Grubbs first generation catalyst” RuCl2(PCy3)2(CHPh) (Cy = cyclohexyl). In a first step, we sequentially polymerized endo,exo[2.2.1]bicyclo-2-ene-5,6-dicarboxylic acid dimethylester with endo,exo[2.2.1]bicyclo-2-ene-5,6-dicarboxylic acid di-tert-butyl ester, to obtain a high control of polymerization and complete characterization of the block copolymers. The polymers were characterized by 1H- and 13C NMR spectroscopy, FT-IR spectroscopy, by GPC, and by DSC. By cleavage of the tert-butyl group, the polymer was transformed into an amphiphilic block copolymer. In two series of polymers, we investigated the micelle formation in ethanol by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). In the first series, the influence of the block ratio on the size of the micelle, the aggregation number, and the core−shell dimensions were investigated while the overall polymer length was kept constant. In the second series, the block ratio was fixed to 1:1 and the overall polymer length was varied, leading to direct proportionality of the micelle size to the polymer length, while the core-to-shell ratio was constant.

Phosphonic acid‐based amphiphilic diblock copolymers derived from ROMP

“…The data represent the actual values correctly only if micelle formation does not occur. 6,16 For example, the most hydrophobic polymer, 4a, was dissolved in DMFd 7 and the 1 H NMR spectrum showed that the integration value of the isopentyl methyl protons were too low, which are caged in the core of the micelle. However, using CDCl 3 or CD 2 Cl 2 the methyl protons appeared in the 1 H NMR spectrum.…”

“…3 Ring-opening metathesis polymerization (ROMP) is a versatile technique for the preparation of well-defined block copolymers with narrow distribution of molecular weights. Several amphiphilic block copolymers obtained by the ROMP pathway have been investigated in the literature and were shown to form micelles and nanoparticles, [4][5][6][7][8][9][10][11][12][13][14] and used as drug delivery materials. [15][16][17] Phosphorus-containing polymers have broad application areas; besides their flameretardant properties, 18 they are also used in biomaterials for their adhesive properties to metals, bone, and dentin.…”

“…The diameter of the micelles can be varied through changes in the composition of the block copolymers while the overall polymer length is kept constant. 6 Three series of block copolymers were synthesized by keeping the molecular weight constant (M n,th ¼ $20,000 g/mol) with varying compositions (4:1; 1:1; 1:4, by weight ratio for monomers 2 and 3). For all of the series, the overall monomer/catalyst ratio was kept constant (60:1).…”

Fiber ‐ and Tube ‐ Formation by Melt Infiltration of Block Copolymers into Al2O3‐Pores

“…A modified literature synthesis [10] was adopted. Synthesis of exo-N-(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)-10-oxa-4-azatricyclodec-8-ene-3,5-dione (monomer D) was done according to the procedure given in reference.…”

Detection of hydrogen peroxide with chemiluminescent micelles

“…In this study, ring opening metathesis polymerization (ROMP) was employed as a new route for the synthesis of amphiphilic peroxalate copolymers. A ROMP-based synthetic strategy was chosen because ROMP is an effi cient and powerful method to synthesize amphiphilic copolymers which have a well-defi ned structure (Stubenrauch et al 2006;Feng et al 2002). In addition, peroxalate esters which are unstable in the presence of nucleophiles and water can tolerate ROMP reaction conditions (Scheme 1).…”