References of "Hedrick, James L"
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See detailNew Functional Aliphatic Polyesters by Chemical Modification of Copolymers of ε-Caprolactone with γ-(2-Bromo-2-methylpropionate)- ε-caprolactone, γ-Bromo- ε-caprolactone, and a Mixture of β-and γ-Ene- ε-caprolactone
Detrembleur, Christophe ULg; Mazza, Michaël; Lou, Xudong et al

in Macromolecules (2000), 33(17), 7751-7760

New functional aliphatic polyesters were prepared by chemical modification of brominated copolyesters. Poly(epsilon-caprolactone)-co-poly(gamma-(2-bromo-2-methylpropionate)-epsilon-caprolactone) copolymer ... [more ▼]

New functional aliphatic polyesters were prepared by chemical modification of brominated copolyesters. Poly(epsilon-caprolactone)-co-poly(gamma-(2-bromo-2-methylpropionate)-epsilon-caprolactone) copolymer was prepared and successfully converted into copolyester bearing methacrylate double bonds by dehydrohalogenation of the pendant tertiary alkyl bromides, thus leading to cross-linkable polyester. The tertiary alkyl bromide groups of the original copolyester were also quaternized by reaction with pyridine, although some side reactions occurred which Limited the reaction yield. Nevertheless, quaternization of the bromide groups of the poly(epsilon-caprolactone)-co-poly(gamma-bromo-epsilon-caprolactone) copolymer proved to be quantitative and to occur without degradation of the polyester chains. This general strategy paves the way to either amphiphilic copolyesters or water-soluble polyesters. The poly(epsilon -caprolactone)-co-poly(gamma -bromo-epsilon-caprolactone) lactone) copolymer was also quantitatively converted into unsaturated copolyester by dehydrohalogenation with formation of double bonds including acrylic-type double bonds. As an alternative, gamma-bromo-epsilon-caprolactone was first dehydrohalogenated, and the unsaturated cyclic monomer was copolymerized with epsilon-caprolactone. Finally, the nonconjugated double bonds of the copolyesters were oxidized into epoxides, except for the acrylic-type unsaturations which remained unchanged. [less ▲]

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See detailFirst example of an unsymmetrical difunctional monomer polymerizable by two living/controlled methods
Mecerreyes, David; Humes, J.; Miller, R. D. et al

in Macromolecular Rapid Communications (2000), 21(11), 779-784

In this paper the synthesis and (co)polymerizations of 4-(acryloyloxy)-epsilon-caprolactone are reported. This new monomer can be polymerized in a living/controlled way by two different polymerization ... [more ▼]

In this paper the synthesis and (co)polymerizations of 4-(acryloyloxy)-epsilon-caprolactone are reported. This new monomer can be polymerized in a living/controlled way by two different polymerization mechanisms: atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP). ATRP, which was carried out at 90 degrees C using NiBr2(PPh3)(2), leads to new polyacrylates containing pendant caprolactone functionalities with controlled molecular weights and narrow polydispersities (M-w/M(p)similar to 1.1). Alternatively, ROP of this functional epsilon-caprolactone bearing a pendant acrylate functionality leads to new poly(4-(acryloyloxy) caprolactone) as well as random copolymers when epsilon-caprolactone and L,L-lactide are added as comonomers. The (co)polymerizations were carried out using either (Al((OPr)-Pr-i)(3) in toluene at 25 degrees C or Sn(Oct)(2) as a catalyst at 110 degrees C producing (co)polymers with controlled molecular weights and narrow polydispersities (M-w/M(n)similar to 1.2). As a potential application, the introduction of acrylate pendant groups into the polyesters facilitated the preparation of cross-linked biodegradable materials either thermally or by irradiation with ultraviolet light radical curing. [less ▲]

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See detailRing-opening polymerization of 6-hydroxynon-8-enoic acid lactone : Novel biodegradable copolymers containing allyl pendent groups
Mecerreyes, David; Miller, Robert D.; Hedrick, James L. et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2000), 38(5), 870-875

This article reports the synthesis and copolymerization of 6-hydroxynon-8-enoic acid lactone. The ring-opening polymerization of this lactone-type monomer bearing a pendant allyl group led to new ... [more ▼]

This article reports the synthesis and copolymerization of 6-hydroxynon-8-enoic acid lactone. The ring-opening polymerization of this lactone-type monomer bearing a pendant allyl group led to new homopolymers and random copolymers with -caprolactone and L,L-lactide. The copolymerizations were carried out at 110 °C with Sn(Oct)2 as a catalyst. The introduction of unsaturations into the aliphatic polyester permitted us to carry out different chemical transformations on this family of polymers. For example, this article reports the bromination, epoxidation, and hydrosylilation of the allyl group in the new polyester copolymers. [less ▲]

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See detailRing-Opening Polymerization of γ-bromo-ε-caprolactone : A novel route to functionalized aliphatic polyesters
Detrembleur, Christophe ULg; Mazza, Michaël; Halleux, Olivier et al

in Macromolecules (2000), 33(1), 14-18

The synthesis, characterization, and polymerization of a new cyclic ester, gamma-bromo-epsilon-caprolactone (gamma-BrCL), are reported. The ring-opening polymerization (ROP) of this new monomer initiated ... [more ▼]

The synthesis, characterization, and polymerization of a new cyclic ester, gamma-bromo-epsilon-caprolactone (gamma-BrCL), are reported. The ring-opening polymerization (ROP) of this new monomer initiated from Al((OPr)-Pr-i)(3) as initiator in toluene at 0 degrees C was found to be living and proceeds by a coordination-insertion mechanism. Random and block copolymerizations of this gamma-BrCL with epsilon-caprolactone (epsilon-CL) were also found to be living as evidenced by the experimental molecular weight which is consistent with that expected from the monomer to initiator molar ratio, the narrow polydispersity, and the good agreement between the comonomers molar fraction in the comonomer feed and the copolymer. The thermal transitions (Tg and Tm) in the epsilon-CL/gamma-Br-CL random copolymers depend strongly on the gamma-BrCL content. Increasing the gamma BrCL content in the copolymer [F(BrCL)] increased the Tg of the copolymer from -61 degrees C for poly(epsilon-caprolactone) to -16.5 degrees C for the poly( gamma-BrCL) homopolymer but decreased the Tm of the PCL to contents of similar to 30 mol % of gamma BrCL [F(BrCL) =0.3]Beyond this value, the copolymers were found to be amorphous and exist as viscous liquids. [less ▲]

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See detailSynthesis of dendritic-linear block copolymers by living ring-opening polymerization of lactones and lactides using dendritic initiators
Mecerreyes, David; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (1999), 37(13), 1923-1930

Polyether dendrons have been successfully used as macroinitiators for the living ring-opening polymerization (ROP) of lactones and lactides. A hydroxyl group located at the focal point of dendrimers of ... [more ▼]

Polyether dendrons have been successfully used as macroinitiators for the living ring-opening polymerization (ROP) of lactones and lactides. A hydroxyl group located at the focal point of dendrimers of different generations was transformed into diethyl aluminum alkoxides by reaction with triethyl aluminum. The dendritic aluminum alkoxides proved to be efficient macroinitiators for the living ROP of -caprolactone (CL), 1,4,8-trioxa(4,6)spiro[9]undecanone (TOSUO), D,L- and L,L-lactide. Formation of these block copolymers of unusual macromolecular architecture was supported by size exclusion chromatography and spectroscopy. The versatility of this synthetic approach allowed -functional dendrimer block-polyesters, such as macromonomer, and macromolecules with novel architectures, to be prepared. [less ▲]

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See detailSynthesis of well-defined poly(alkyl methacrylate)-graft-polylactone by sequential living polymerization
Mecerreyes, David; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Macromolecular Chemistry and Physics (1999), 200(1), 156-165

A novel combination of living polymerization reactions has been proposed for the controlled synthesis of poly(alkyl methacrylate)-graft-polylactones. This strategy relies upon the sequential living ... [more ▼]

A novel combination of living polymerization reactions has been proposed for the controlled synthesis of poly(alkyl methacrylate)-graft-polylactones. This strategy relies upon the sequential living polymerization of alkyl methacrylates and aliphatic lactones, with an intermediate chemical transformation for shifting from the first mechanism to the second one. In the first step, an alkyl methacrylate (methyl and butyl) is copolymerized with 2-trimethylsiloxyethyl methacrylate (TMSEMA). This living anionic polymerization is initiated with diphenylhexyllithium( DPHLi) in the presence of a μ-ligand, lithium chloride, in THF at - 78 °C. The trimethylsiloxy groups are then hydrolyzed with release of hydroxyl groups which are reacted with triethylaluminum in order to form a multifunctional macroinitiator of the Al alkoxide type. The second step consists of the ring opening polymerization (ROP) of aliphatic lactones (ε-caprolactone, J-valerolactone and 1,4,8-trioxaspiro[4.6]-9-undecanone (TOSUO)) with the formation of novel graft copolymers. As a result of the livingness of both the anionic and the ROP polymerization steps, the molecular weight of both the main backbone and the grafts is predictable, the apparent polydispersity is narrow ( from 1.05 to 1.30) and the grafting density can be controlled being dependent on the distribution of the hydroxyl groups within the precursor backbone. [less ▲]

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See detailDendrimer-like star block and amphiphilic copolymers by combination of ring opening and atom transfer radical polymerization
Hedrick, James L.; Trollsas, Mikael; Hawker, Craig Jon et al

in Macromolecules (1998), 31(25), 8691-8705

A new type of macromolecular architecture, denoted as dendrimer-like star block copolymers, is reported. These block copolymers are described by a radial geometry where the different generations or layers ... [more ▼]

A new type of macromolecular architecture, denoted as dendrimer-like star block copolymers, is reported. These block copolymers are described by a radial geometry where the different generations or layers are comprised of high molecular weight polymer emanating from a central core. A hexahydroxyl functional core was used as an initiator for the “living” ring opening polymerization (ROP) of ε-caprolactone producing a hydroxyl terminated six arm star polymer with controlled molecular weight and narrow polydispersities (PD < 1.1). Capping these chain ends with dendrons containing activated bromide moieties produced “macro-initiators” for atom transfer radical polymerization (ATRP). Methyl methacrylate was polymerized from these “macro-initiators” in the presence of an organometallic promoter to produce the requisite dendrimer-like star polymers. High molecular weight was obtained with low polydispersities (<1.2). Alternatively, amphiphilic character could be introduced by designing the different layers or generations to be either hydrophobic or hydrophilic. For example, methyl methacrylate (MMA) with either hydroxyethyl methacrylate (HEMA) or methacrylate functional ethylene oxide macromonomers (EO) were polymerized from these “macro-initiators” to provide a hydrophilic outer layer. The use of macromolecular building blocks allows rapid attainment of high polymer in a limited number of steps with purification between transformation requiring only polymer precipitation. [less ▲]

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See detailInternal functionalization in hyperbranched polyesters
Trollsas, Michaël; Hedrick, James L.; Mecerreyes, David et al

in Journal of Polymer Science. Part A, Polymer Chemistry (1998), 35(17), 3187-3192

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See detailSynthesis of novel polymeric materials based on aliphatic polyesters by combination of different controlled polymerization methods
Jérôme, Robert ULg; Mecerreyes, David; Tian, Dong et al

in Macromolecular Symposia (1998), 132

Combination of the living ring-opening polymerization (ROP) of ε-CL and lactides with the "controlled" free radical polymerization of styrene and methacrylic monomers is a versatile strategy for the ... [more ▼]

Combination of the living ring-opening polymerization (ROP) of ε-CL and lactides with the "controlled" free radical polymerization of styrene and methacrylic monomers is a versatile strategy for the synthesis of well-defined block and graft copolymers. In this respect, the dual "living" polymerization strategy in which two different functional groups on a single molecule used to initiate the two controlled mechanisms is particularly efficient. Combination of ROP and step-growth polymerization is another versatile methodology for the preparation of a large variety of new materials, e.g. polyimide nanofbams, polyester/silica hybrid materials and star and branched polyesters by dendritic initiation. [less ▲]

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See detailSynthesis of acid-functional asymmetric aliphatic polyesters
Trollsas, Michael; Hedrick, James L; Dubois, Philippe ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (1998), 36(8), 1345-1348

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See detailSimultaneous dual living polymerizations: a novel one-step approach to block and graft copolymers
Mecerreyes, David; Moineau, Georges; Dubois, Philippe ULg et al

in Angewandte Chemie (International ed. in English) (1998), 37(9), 1274-1276

Just one step is required for the synthesis of block copolymers by simultaneous living/controlled ring-opening and radical polymerization initiated by a difunctional (A-B) compound (shown schematically on ... [more ▼]

Just one step is required for the synthesis of block copolymers by simultaneous living/controlled ring-opening and radical polymerization initiated by a difunctional (A-B) compound (shown schematically on the right). [less ▲]

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See detailHighly functional branched and dendri-graft aliphatic polyesters through ring opening polymerization
Trollsas, Michaël; Hedrick, James L.; Mecerreyes, David et al

in Macromolecules (1998), 31(9), 2756-2763

Highly branched poly(ε-caprolactones) with novel and well-defined molecular architectures have been synthesized by the use of new multifunctional initiators. The ring-opening polymerization methods used ... [more ▼]

Highly branched poly(ε-caprolactones) with novel and well-defined molecular architectures have been synthesized by the use of new multifunctional initiators. The ring-opening polymerization methods used to prepare these new structures allowed accurate control of molecular weight and narrow molecular weight distributions. In addition, the synthesis of even more complex molecular architectures was possible by the use of 1,4,9-trioxaspiro[4.6]-9-undecanone as a comonomer with ε-caprolactone. After copolymerization, complete deacetalization of the polyester chains into the corresponding ketone groups followed by quantitative reduction formed polymers with hydroxyl pendant groups. With this synthetic strategy, significant additional functionality was introduced. In addition, the pendant hydroxyl groups along the chains can serve as macroinitiators for the further initiation of ε-caprolactone to prepare dendri-graft molecular architectures. The new polymers were characterized by 1H NMR, 13C NMR, and size exclusion chromatography (SEC). 13C NMR spectra clearly showed that the hydroxyl groups of the initiators were fully substituted to give polymers with two, four, and six arms. [less ▲]

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See detailDual living free radical and ring opening polymerizations from a double-headed initiator
Hawker, Craig J; Hedrick, James L; Malmström, Eva E et al

in Macromolecules (1998), 31(2), 213-219

The concept of performing dual living polymerizations from a single initiating molecule with no intermediate activation, or transformation, steps is presented. The compatibility of “living”, or controlled ... [more ▼]

The concept of performing dual living polymerizations from a single initiating molecule with no intermediate activation, or transformation, steps is presented. The compatibility of “living”, or controlled free radical procedures, either nitroxide mediated or atom transfer radical polymerization (ATRP), with the living ring opening polymerization of ε-caprolactone, and vice versa, is demonstrated by the synthesis of a variety of well-defined block copolymers. For example, from a hydroxy-functionalized alkoxyamine, either the living ring opening polymerization of ε-caprolactone, or the “living” free radical polymerization of styrene can be performed leading to narrow polydispersity polymeric initiators. These polymeric initiators can then be used to initiate the living polymerization of the other monomer system without the need for intermediate steps. In a similar way, hydroxy-functionalized ATRP initiators can be used as bifunctional initiators for the polymerization of both ε-caprolactone and a variety of other vinyl monomers. The novel block copolymers that are obtained were shown to have low polydispersities and controllable molecular weights for both of the blocks. [less ▲]

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See detailPolyimide nanofoams from aliphatic polyester-based copolymers
Hedrick, James L; Carter, K. R.; Richter, R. et al

in Chemistry of Materials (1998), 10(1), 39-49

High-temperature polymeric foams were prepared using compositionally asymmetric microphase-separated block copolymers where the major component is thermally stable and the minor component is thermally ... [more ▼]

High-temperature polymeric foams were prepared using compositionally asymmetric microphase-separated block copolymers where the major component is thermally stable and the minor component is thermally labile. Upon thermal treatment, the dispersed phase undergoes thermolysis leaving pores the size and shape of which are dictated by the initial copolymer morphology. The driving force behind the survey of aliphatic polyesters as possible labile blocks stems from their quantitative degradation into low-boiling, polar degradation products. Poly(lactones), as a general class of materials, degrade by a backbiting process producing, primarily, monomer and cyclic oligomers. A ring-opening synthetic route to poly(lactones) affords oligomers of predictable molecular weight, narrow molecular weight distribution, and controlled end-group functionality. Block copolymers were prepared using monofunctional caprolactone and valerolactone oligomers and a high-Tg polyimide. Microphase separation was observed in all cases, and the lactone blocks did not crystallize. Thermal decomposition of the caprolactone block was accomplished by heating the copolymer to 370 °C for 5 h. Significant density reductions were found with pore sizes in the 60−70 Å range. [less ▲]

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See detailVersatile and controlled synthesis of star and branched macromolecules by dentritic initiation
Trollsas, Michaël; Hedrick, James L.; Mecerreyes, David et al

in Macromolecules (1997), 30(26), 8508-8511

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See detailLiving free radical polymerization of macromonomers: preparation of well defined graft copolymers
Hawker, Craig Jon; Mecerreyes, David; Elce, Edmund et al

in Macromolecular Chemistry and Physics (1997), 198(1), 155-166

Well defined graft copolymers have been synthesized by a nitroxide-mediated "living" free radical process using pre-formed macromonomers. Analysis of the graft systems revealed that the macromonomer was ... [more ▼]

Well defined graft copolymers have been synthesized by a nitroxide-mediated "living" free radical process using pre-formed macromonomers. Analysis of the graft systems revealed that the macromonomer was efficiently incorporated into the polymeric back-bone to give block copolymers of controlled molecular weight and narrow polydispersi-ties. An added benefit of the "living" free radical process is that macromonomers, such as polylactide or polycaprolactone, which contain reactive functional groups can be used to form novel graft Systems using this approach. Functionalized monomers or polymeric initiators were also used in the copolymerization mixture to give graft Systems with a variety of functional groups attached to the backbone. [less ▲]

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See detailPolyimide foams derived from a high Tg polyimide with grafted poly(α-methylstyrene)
Hedrick, James L; DiPietro, R.; Plummer, C. J. G. et al

in Polymer (1996), 37(23), 5229-5236

A new route to high-Tg, thermally stable polyimide foams has been developed. Foams were prepared by casting microphase-separated graft copolymers comprising a thermally stable main chain, polyimide, and a ... [more ▼]

A new route to high-Tg, thermally stable polyimide foams has been developed. Foams were prepared by casting microphase-separated graft copolymers comprising a thermally stable main chain, polyimide, and a thermally labile graft, poly(α-methylstyrene). The copolymer compositions were designed so that the thermally labile block would be the dispersed phase. This can unzip to its monomer upon heating, and the decomposition product diffuses out of the film, leaving pores embedded in a matrix of the thermally stable component. The copolymers were synthesized through either the poly(amic acid) precursor, followed by chemical cyclodehydration to the imide form, or the poly(amic alkyl ester) precursor followed by thermal imidization. The decomposition of the α-methylstyrene in the block copolymer was studied by thermogravimetric, dynamic mechanical and thermomechanical analyses. Mild decomposition conditions were required to avoid rapid depolymerization of the α-methylstyrene and excessive plasticization of the polyimide matrix. The foams showed pore sizes with diameters ranging from less than 20 nm to over 1 µm, depending upon the synthetic route employed, and the reduction in the mass density was generally consistent with the starting composition. [less ▲]

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See detailHigh-temperature polyimide nanofoams for microelectronic applications
Hedrick, James L; Carter, K. R.; Cha, J. E. et al

in Reactive & Functional Polymers (1996), 30(1-3), 43-53

Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the ... [more ▼]

Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range, thus, the term 'nanofoam'. The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials were investigated as well as from a number of thermally labile polymers. The foams were characterized by a variety of experiments including TEM, SAXS, WAXD, DMTA, density measurements. refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and low dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach. [less ▲]

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See detailPolyimide nanofoams from caprolactone-based copolymers
Hedrick, James L; Russell, T. P.; Sanchez, M. et al

in Macromolecules (1996), 29(10), 3642-3646

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