Experimental and theoretical investigation of the lamellar structure of a styrene-butyl methacrylate diblock copolymer by fluorescence resonance energy transfer, small-angle X-ray scattering, and self-consistent-field simulations

in Macromolecules (2006), 39(20), 7055-7063

We have investigated the repeat distance and interface thickness, at 160 degrees C, of a poly(styrene-b-butyl methacrylate) (PS-b-PBMA) diblock copolymer of similar to 180 000 molecular weight by small ... [more ▼]

We have investigated the repeat distance and interface thickness, at 160 degrees C, of a poly(styrene-b-butyl methacrylate) (PS-b-PBMA) diblock copolymer of similar to 180 000 molecular weight by small- angle X-ray scattering (SAXS) and fluorescence resonance energy transfer ( FRET). We have found a lamellar period of 47 nm and an interface thickness of 5 nm. A simple, hyperbolic secant model of the junction distribution appeared to be sufficient to analyze the fluorescence decay data on the junction-labeled polymer containing different acceptor/donor ratios, but simulations based on a numerical self- consistent-field (NSCF) formalism also allowed us to find a range of approximately 0.017-0.018 for the Flory-Huggins interaction parameter (chi(FH), defined with reference to the monomeric volume of polystyrene) and a PBMA Kuhn length (b(PBMA)) of 0.65-0.67 nm. We note that earlier values of chi(FH) and b(PBMA) reported in the literature vary considerably. The NSCF computations suggest that even modest levels of conformational asymmetry perturb the block copolymer morphology. A weakness of our theoretical (NSCF) approach is the compressible nature of PS-b-PBMA. However, lattice cluster, equation of state (EOS), or other models that allow for compressibility have not yet been developed to the level of sophistication needed to predict block copolymer repeat distances or interface thicknesses. Indeed, as detailed in the Supporting Information, current EOS methods leave much to be desired even in predicting the phase transitions of lower molecular weight PS-b-PBMA samples. [less ▲]

Stable free radical polymerization of acrylates promoted by α-hydroxycarbonyl compounds

in Macromolecules (2006), 39(16), 5359-5363

The living-radical polymerization of n-butyl acrylate, moderated with TEMPO, is shown to proceed in a controlled fashion in the presence of a series of α-hydroxycarbonyl compounds with different organic ... [more ▼]

The living-radical polymerization of n-butyl acrylate, moderated with TEMPO, is shown to proceed in a controlled fashion in the presence of a series of α-hydroxycarbonyl compounds with different organic bases. The best results were obtained with glyceraldehyde dimer in the presence of pyridine. These results further support the suggestion that the difficulty of polymerizing acrylate monomers in the presence of TEMPO is related to the excess buildup of TEMPO due to a small amount of polymer chain termination and to a lesser extent on the higher bond dissociation energy of the TEMPO acrylate bond relative to the TEMPO styrene bond at the chain's terminus. [less ▲]

First Insights into Electrografted Polymers by AFM-Based Force Spectroscopy

in Macromolecules (2006), 39

The very first characterization of the structural properties of polymer films obtained by electrografting is reported. AFM-based force spectroscopy was used to investigate poly-N-succinimidyl acrylate ... [more ▼]

The very first characterization of the structural properties of polymer films obtained by electrografting is reported. AFM-based force spectroscopy was used to investigate poly-N-succinimidyl acrylate (PNSA) layers electrografted directly from a silicon substrate. Quantitative analysis of compression profiles obtained in a good solvent and single molecule bridging interaction, in light of the Alexander-de Gennes model, gave access to the grafting density and degree of polymerization. A high swelling capacity has been evidenced. This report is the first evidence that polymers obtained by cathodic electrografting are in fact brush systems, and consequently the first evidence that a polymer brush can be obtained from a direct “grafting from” method, without any intermediate layer. [less ▲]

Controlled synthesis of an ABC miktoarm star-shaped copolymer by sequential ring-opening polymerization of ethylene oxide, benzyl beta-malolactonate, and epsilon-caprolactone

in Macromolecules (2005), 38(26), 10650-10657

This paper reports on the synthesis of an amphiphilic miktoarm ABC star-shaped copolymer, s[(PEO)(PMLABz)(PCL)], consisting of biocompatible/bioresorbable arms. Indeed, PEO is a hydrophilic biocompatible ... [more ▼]

This paper reports on the synthesis of an amphiphilic miktoarm ABC star-shaped copolymer, s[(PEO)(PMLABz)(PCL)], consisting of biocompatible/bioresorbable arms. Indeed, PEO is a hydrophilic biocompatible poly(ethylene oxide) arm, PMLABz is a poly(benzyl beta-malolactonate) arm precursor of a pH-sensitive bioresorbable poly(beta-malic acid) block, and PCL is a hydrophobic bioresorbable poly(epsilon-caprolactone) arm. Each constitutive arm was prepared by ring-opening polymerization. A double-headed PEO macroinitiator [PEO-(OH)-COO-K+] was first prepared by selective hydrolysis of the alpha-lactone (2-oxepanone) end group of PEO chains end-capped by a omega-methoxy group. The anionic polymerization of benzyl beta-malolactonate (MLABz) was selectively initiated by the alpha-potassium carboxylate end group of PEO in the presence of 18-crown-6 ether. The polymerization of epsilon-caprolactone (epsilon-CL) was initiated by the hydroxyl group left at the junction of the two blocks of the as-prepared PEO-b-PMLABz diblock copolymer, in the presence of tin(II) bis(2-ethylhexanoate) (Sn(Oct)(2)). The macroinitiator, the intermediate diblock, and the final miktoarm. star-shaped copolymer were analyzed by H-1 NMR spectroscopy and size exclusion chromatography. [less ▲]

Quinone transfer radical polymerization of styrene catalyzed by metal complexes in the presence of various o-quinones

in Macromolecules (2005), 38(15), 6310-6315

Several o-quinones have been tested as control agents for the quinone transfer radical polymerization (QTRP) of styrene in the presence of cobalt(II) acetylacetonate. In contrast to the commercially ... [more ▼]

Several o-quinones have been tested as control agents for the quinone transfer radical polymerization (QTRP) of styrene in the presence of cobalt(II) acetylacetonate. In contrast to the commercially available 3,5-di-tert-butyl-o-benzoquinone (3,5-DtBBQ) and tetrachloro-1,2-benzoquinone (tetrachloro-1,2-BQ), 3,6-dimethoxy-9,10-phenanthrenequinone (3,6-DMPhQ) imparts a better control to the radical polymerization of styrene compared to 9,10-phenanthrenequinone (PhQ) used as a reference. Indeed, whenever 3,6-DMPhQ is added with a catalytic amount of metal complexes (Co(acac)(2) or Al(acac)(3)), the evolution of the molar mass with the monomer conversion is linear, and low polydispersity (M-w/M-n similar to 1.1-1.2) is observed until very high monomer conversion (similar to 90%). Finally, the methoxy protons of 3,6-DMPhQ have been detected by H-1 NMR analysis of the polystyrene end groups, which is important mechanistic information. [less ▲]

Controlled radical polymerization of styrene by quinone transfer radical polymerization (QTRP)

in Macromolecules (2005), 38(1), 27-32

Radical polymerization of styrene falls under control when conducted at 100 degreesC, in the presence of an ortho-quinone, e.g., phenanthrenequinone (PhQ): and a catalytic amount of cobalt(II ... [more ▼]

Radical polymerization of styrene falls under control when conducted at 100 degreesC, in the presence of an ortho-quinone, e.g., phenanthrenequinone (PhQ): and a catalytic amount of cobalt(II) acetylacetonate. Criteria for a controlled chain polymerization are fulfilled at least until 50% of monomer conversion, i.e., molar mass increasing with monomer conversion. molar mass predictable from the styrene/ quinone molar ratio, linear time dependence of ln([M](o)/[M]), and effective resumption of Styrene polymerization by preformed oligopolystyrene. A tentative mechanism is proposed for this new System designated as quinone transfer radical polymerization (QTRP). [less ▲]

Formation of polyamide 12-polyisoprene core-shell particles in polystyrene by reactive blending

in Macromolecules (2004), 37(14), 5317-5322

Polyamide 12 (PA12)-polyisoprene (PIP) particles with a thermoplastic core and a rubbery shell have been prepared in a thermoplastic matrix (PS) by reactive blending. For this purpose, an anhydride-end ... [more ▼]

Polyamide 12 (PA12)-polyisoprene (PIP) particles with a thermoplastic core and a rubbery shell have been prepared in a thermoplastic matrix (PS) by reactive blending. For this purpose, an anhydride-end-capped PS-b-PIP diblock (PS-b-PIP-anh) has been reacted with PA12 chains end-capped (50% of them) by a primary amine and dispersed in PS. A PS-b-PIP-PA12 triblock has been formed at the interface between the PS matrix and the dispersed PA12 microdomains. Thus, the phase morphology consists of PA12 core-PIP shell particles dispersed in PS. The nonreacted PA12 with respect to PS-b-PIP-anh dictates the size of the polyamide (core) domains, and the reactive diblock (mainly the molecular weight of the PIP block) imposes the shell thickness and modulates the core size by its capacity to compatibilize PA12 and the thermoplastic matrix. [less ▲]

Nanostructured polyamide by reactive blending. 1. Effect of the reactive diblock composition

in Macromolecules (2004), 37(9), 3459-3469

Reactive blending of phthalic anhydride end-capped polystyrene-b-polyisoprene diblock (PS-b-PIP-anh) with 80 wt % of polyamide 12 (PA12) results in the very rapid formation of a PS-b-PIP-b-PA triblock ... [more ▼]

Reactive blending of phthalic anhydride end-capped polystyrene-b-polyisoprene diblock (PS-b-PIP-anh) with 80 wt % of polyamide 12 (PA12) results in the very rapid formation of a PS-b-PIP-b-PA triblock copolymer, which self-assembles with formation of characteristic nanoobjects, within the polyamide matrix. For instance, a vesicular nanostructure is formed in the particular case of a symmetric, lamellar-forming diblock copolymer. This morphology actually complies with the lower curvature possible for ABC lamellae diluted in a continuous C phase under shear. In contrast, when the diblock composition is typically asymmetric (at constant molecular weight), vesicles disappear in favor of a core-shell morphology with a cucumber-like suborganization. This spontaneous nanostructuration of the PA12 matrix is quite general. Indeed substitution of an amorphous primary amine end-capped styrene/acrylonitrile random copolymer (SAN-NH2) for PA12 results in exactly the same phase morphology upon reactive blending with PS-b-PIP-anh. [less ▲]

Polymerization of epsilon-caprolactone initiated by Y alkoxide grafted onto porous silica

in Macromolecules (2003), 36(19), 7094-7099

Ring-opening polymerization of c-caprolactone has been initiated by Y isopropoxide grafted onto silica, in the presence of 2-propanol, in toluene at 40degreesC. The degree of polymerization is controlled ... [more ▼]

Ring-opening polymerization of c-caprolactone has been initiated by Y isopropoxide grafted onto silica, in the presence of 2-propanol, in toluene at 40degreesC. The degree of polymerization is controlled by the initial monomer/(alcohol + alkoxide) molar ratio. Deactivation of the chains by an alcohol is essential for them to be detached from the support and to be collected totally free of metal and silica residues. The alkoxide is also regenerated at the surface of the support, which allows for recycling the catalyst. [less ▲]

Polymer coating of steel by a combination of electrografting and atom-transfer radical polymerization

in Macromolecules (2003), 36(16), 5926-5933

Cathodic electrografting of poly(2-chloropropionate ethyl acrylate) (poly[cPEA]) onto steel followed by the styrene grafting-from by atom transfer radical polymerization (ATRP) is an efficient strategy to ... [more ▼]

Cathodic electrografting of poly(2-chloropropionate ethyl acrylate) (poly[cPEA]) onto steel followed by the styrene grafting-from by atom transfer radical polymerization (ATRP) is an efficient strategy to impart strong adhesion to polystyrene films onto the electrically conductive substrate. Electrografting of poly(cPEA) chains at an appropriate potential and persistence of the activated chloride in the grafted chains were confirmed by XPS. Polystyrene deposition by ATRP with a ruthenium-based catalyst was analyzed by scanning electron microscopy and Raman spectroscopy. Adhesion of the polystyrene layer to the substrate is so strong that it cannot be detached by standard Scotch brand tapes. Moreover, local thermal analysis showed a loss of mobility for the PS chains tethered at the surface. [less ▲]