David Lohse - Academia.edu (original) (raw)

Papers by David Lohse

Research paper thumbnail of Well-Defined, Model Long Chain Branched Polyethylene. 2. Melt Rheological Behavior

Macromolecules, Mar 9, 2002

Research paper thumbnail of Pressure-Volume-Temperature properties of polyolefin liquids and their melt miscibility

Journal of Polymer Science Part B, Oct 15, 1999

Research paper thumbnail of Scattering from Polymers

Acs Symposium Series, Jul 30, 1999

Research paper thumbnail of The Critical Role of Anionic Polymerization for Advances in the Physics of Polyolefins

Springer eBooks, 2015

This chapter shows how the great power and versatility of anionic polymerization, which has been ... more This chapter shows how the great power and versatility of anionic polymerization, which has been described in the rest of this book, has been used to develop an improved understanding of the basic physical principles that underlie the performance of polyolefin materials. When these synthetic tools are employed to polymerize dienes and are then combined with controlled saturation methods, a wide panoply of saturated hydrocarbon polymers can be made. These products can serve as models for commercial polyolefins, which is the most widely used class of synthetic polymers and which continues to develop at a strong pace. The ability to make such models with highly controlled chain architectures, plus the ability to label the molecules for use in techniques such as NMR and neutron scattering, has provided polymer physicists with means to understand polyolefin physics at a deep level. This has been used to determine the size of polyolefin chains (both in dilute solution and in melt state), the ways that polyolefins mix, how their rheology depends on the chemical structure of the chains, and how long branches control their performance. This chapter covers not only the scientific results of this research, but also how these can be applied in the development of novel, useful polyolefin products.

Research paper thumbnail of Highly Ordered Supramolecular Structures from Self-Assembly of Ionic Surfactants in Oppositely Charged Polyelectrolyte Gels

Acs Symposium Series, Jul 23, 1999

Research paper thumbnail of Morphologies of blends of isotactic polypropylene and ethylene copolymer by rapid expansion of supercritical solution and isobaric crystallization from supercritical solution

Journal of Applied Polymer Science, 2000

ABSTRACT Isotactic polypropylene (iPP) and ethylene-butene (EB) copolymers were dissolved in supe... more ABSTRACT Isotactic polypropylene (iPP) and ethylene-butene (EB) copolymers were dissolved in supercritical propane and precipitated by rapid expansion of supercritical solution (RESS) and isobaric crystallization from SS (ICSS). The cloud-point pressures of the ternary solutions were found to increase as the immiscibility of PP and EB copolymer increased (i.e., as the number of ethyl branches in the EB copolymers decreased). The RESS process resulted in microfibers and a trace of microparticles, and the EB copolymer domains in the blends decreased in size as the ethyl branch content in the EB copolymers increased. The thermal stability of the copolymer domains was improved by synthesizing thermoplastic vulcanizate (TPV) from PP and ethylene-propylene-diene terpolymer in a supercritical propane solution followed by RESS. The ICSS process produced microcellular polymeric foamlike materials, but the two polymers were precipitated independently by thermally induced phase separation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1478–1487, 2000

Research paper thumbnail of Blends of amorphous-crystalline block copolymers with amorphous homopolymers. Morphological studies by electron microscopy and small angle scattering

Research paper thumbnail of Thermoplastic Vulcanizates from Isotactic Polypropylene and Ethylene−Propylene−Diene Terpolymer in Supercritical Propane: Synthesis and Morphology

Macromolecules, Jul 23, 1998

ABSTRACT New thermoplastic vulcanizates (TPV's) have been synthesized from isotactic poly... more ABSTRACT New thermoplastic vulcanizates (TPV's) have been synthesized from isotactic polypropylene and ethylene−propylene−diene terpolymer (EPDM) in a supercritical propane solution. The ternary solution of polypropylene and EPDM in supercritical propane exhibited less solubility than the corresponding binary solutions of polypropylene or EPDM separately in propane. Higher pressure in the supercritical polymer solution enhanced the mutual solubility of the two polymers. EPDM was cross-linked with tert-butyl peroxide while in supercritical solution. On lowering the pressure while remaining above the melting temperature of the polymers, the supercritical TPV gel phase separated in a manner consistent with spinodal decomposition. On isobaric cooling of the supercritical TPV gel, the polypropylene crystallized, freezing the morphology. The cross-linking of EPDM in the homogeneous supercritical propane solutions was found to be nearly complete. The final TPV's were phase separated, exhibiting two melting transitions. The morphology of the TPV's was a microporous, apparently closed-cell polymeric foam. Phase contrast optical microscopy showed micro-heterogeneous EPDM domains dispersed in the polypropylene matrix for the TPV's. The phase domain sizes were much smaller, by a factor of 5−10 or so, than those of the corresponding melt blends.

Research paper thumbnail of Polyolefins

Research paper thumbnail of Anomalous mixing behavior of polyisobutylene with other polyolefins

Macromolecules, Feb 1, 1995

ABSTRACT: Mutual solubilities and liquid-state interactions of polyisobutylene (PIB) with other p... more ABSTRACT: Mutual solubilities and liquid-state interactions of polyisobutylene (PIB) with other polyolefins were investigated by a variety of techniques. Near room temperature PIB was found to be miscible with a limited range of polyolefin structures. The interactions for several blends in this range were determined by small-angle neutron scattering. The Flory-Huggins parameter x was found to be large and negative at room temperature in all cases, contrary to expectations and to previous experience with blends of other saturated ...

Research paper thumbnail of Crystallization Kinetics and Microdomain Structures for Blends of Amorphous-Crystalline Block Copolymers with Amorphous Homopolymers

Springer eBooks, 1994

Blends of a symmetrical diblock poly(ethylene-b-propylene) (DEP) and an atactic polypropylene (AP... more Blends of a symmetrical diblock poly(ethylene-b-propylene) (DEP) and an atactic polypropylene (APP) were studied by calorimetry, small angle neutron scattering, and electron microscopy. Addition of APP to DEP drastically changed the crystallization kinetics of the polyethylene block. The results were interpreted on the basis of the morphological studies of the microdomain structure in both the crystalline state and the melt state of the blends.

Research paper thumbnail of Compatibility and morphology of blends of isotactic and atactic polypropylene

Journal of Materials Science, Feb 1, 1991

Research paper thumbnail of Short Communication: Three Selected as PMSE Fellows in 2004

Polymer News, May 1, 2004

... in 2004 David J. Lohse ExxonMobil Research and Engineering Co. ... Nikos Hadjichristidis Bill... more ... in 2004 David J. Lohse ExxonMobil Research and Engineering Co. ... Nikos Hadjichristidis Bill MacKnight Don Schulz They were inducted as the fifth class of PMSE Fellows during the Awards Lunch at the Anaheim ACS Meeting on Monday, March 29th, 2004. ...

Research paper thumbnail of The configurational statistics of a polymeric chain confined by impenetrable barriers. II. The floating chain

Journal of Chemical Physics, Apr 15, 1977

ABSTRACT

Research paper thumbnail of Short Chain Branching Effect on the Cloud-Point Pressures of Ethylene Copolymers in Subcritical and Supercritical Propane

Macromolecules, Mar 26, 1998

Research paper thumbnail of Interfacial Aspects of Multicomponent Polymer Materials

Research paper thumbnail of Polymeric Compatibilizers: Uses and Benefits in Polymer Blends

Research paper thumbnail of Dynamic viscoelastic properties of poly(ethylene-propylene) diblock copolymer in the melt state and solutions

Research paper thumbnail of Structure Characterization in the Science and Technology of Elastomers

Publisher Summary This chapter discusses structure characterization in the science and technology... more Publisher Summary This chapter discusses structure characterization in the science and technology of elastomers. The chemical elemental analysis of polymers can often be carried out by the methods used for low-molecular-weight organic compounds. This is particularly true when combustion of the sample is involved. Thus, C, H, and N can be determined on milligram samples by complete combustion followed by gas chromatographie analysis of the gases evolved. Accuracy is about 0.3%. Quite often the composition of an elastomer is only an average of a wide distribution of structures. It can be a composite of polymer, additives, and impurities, and if the polymer itself contains more than one type of monomer unit, a variety of polymer compositions are possible. These can be distributed inter- and intramolecularly.

Research paper thumbnail of Graft Copolymers

Encyclopedia of Polymer Science and Technology, 2010

Research paper thumbnail of Well-Defined, Model Long Chain Branched Polyethylene. 2. Melt Rheological Behavior

Macromolecules, Mar 9, 2002

Research paper thumbnail of Pressure-Volume-Temperature properties of polyolefin liquids and their melt miscibility

Journal of Polymer Science Part B, Oct 15, 1999

Research paper thumbnail of Scattering from Polymers

Acs Symposium Series, Jul 30, 1999

Research paper thumbnail of The Critical Role of Anionic Polymerization for Advances in the Physics of Polyolefins

Springer eBooks, 2015

This chapter shows how the great power and versatility of anionic polymerization, which has been ... more This chapter shows how the great power and versatility of anionic polymerization, which has been described in the rest of this book, has been used to develop an improved understanding of the basic physical principles that underlie the performance of polyolefin materials. When these synthetic tools are employed to polymerize dienes and are then combined with controlled saturation methods, a wide panoply of saturated hydrocarbon polymers can be made. These products can serve as models for commercial polyolefins, which is the most widely used class of synthetic polymers and which continues to develop at a strong pace. The ability to make such models with highly controlled chain architectures, plus the ability to label the molecules for use in techniques such as NMR and neutron scattering, has provided polymer physicists with means to understand polyolefin physics at a deep level. This has been used to determine the size of polyolefin chains (both in dilute solution and in melt state), the ways that polyolefins mix, how their rheology depends on the chemical structure of the chains, and how long branches control their performance. This chapter covers not only the scientific results of this research, but also how these can be applied in the development of novel, useful polyolefin products.

Research paper thumbnail of Highly Ordered Supramolecular Structures from Self-Assembly of Ionic Surfactants in Oppositely Charged Polyelectrolyte Gels

Acs Symposium Series, Jul 23, 1999

Research paper thumbnail of Morphologies of blends of isotactic polypropylene and ethylene copolymer by rapid expansion of supercritical solution and isobaric crystallization from supercritical solution

Journal of Applied Polymer Science, 2000

ABSTRACT Isotactic polypropylene (iPP) and ethylene-butene (EB) copolymers were dissolved in supe... more ABSTRACT Isotactic polypropylene (iPP) and ethylene-butene (EB) copolymers were dissolved in supercritical propane and precipitated by rapid expansion of supercritical solution (RESS) and isobaric crystallization from SS (ICSS). The cloud-point pressures of the ternary solutions were found to increase as the immiscibility of PP and EB copolymer increased (i.e., as the number of ethyl branches in the EB copolymers decreased). The RESS process resulted in microfibers and a trace of microparticles, and the EB copolymer domains in the blends decreased in size as the ethyl branch content in the EB copolymers increased. The thermal stability of the copolymer domains was improved by synthesizing thermoplastic vulcanizate (TPV) from PP and ethylene-propylene-diene terpolymer in a supercritical propane solution followed by RESS. The ICSS process produced microcellular polymeric foamlike materials, but the two polymers were precipitated independently by thermally induced phase separation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1478–1487, 2000

Research paper thumbnail of Blends of amorphous-crystalline block copolymers with amorphous homopolymers. Morphological studies by electron microscopy and small angle scattering

Research paper thumbnail of Thermoplastic Vulcanizates from Isotactic Polypropylene and Ethylene−Propylene−Diene Terpolymer in Supercritical Propane: Synthesis and Morphology

Macromolecules, Jul 23, 1998

ABSTRACT New thermoplastic vulcanizates (TPV's) have been synthesized from isotactic poly... more ABSTRACT New thermoplastic vulcanizates (TPV's) have been synthesized from isotactic polypropylene and ethylene−propylene−diene terpolymer (EPDM) in a supercritical propane solution. The ternary solution of polypropylene and EPDM in supercritical propane exhibited less solubility than the corresponding binary solutions of polypropylene or EPDM separately in propane. Higher pressure in the supercritical polymer solution enhanced the mutual solubility of the two polymers. EPDM was cross-linked with tert-butyl peroxide while in supercritical solution. On lowering the pressure while remaining above the melting temperature of the polymers, the supercritical TPV gel phase separated in a manner consistent with spinodal decomposition. On isobaric cooling of the supercritical TPV gel, the polypropylene crystallized, freezing the morphology. The cross-linking of EPDM in the homogeneous supercritical propane solutions was found to be nearly complete. The final TPV's were phase separated, exhibiting two melting transitions. The morphology of the TPV's was a microporous, apparently closed-cell polymeric foam. Phase contrast optical microscopy showed micro-heterogeneous EPDM domains dispersed in the polypropylene matrix for the TPV's. The phase domain sizes were much smaller, by a factor of 5−10 or so, than those of the corresponding melt blends.

Research paper thumbnail of Polyolefins

Research paper thumbnail of Anomalous mixing behavior of polyisobutylene with other polyolefins

Macromolecules, Feb 1, 1995

ABSTRACT: Mutual solubilities and liquid-state interactions of polyisobutylene (PIB) with other p... more ABSTRACT: Mutual solubilities and liquid-state interactions of polyisobutylene (PIB) with other polyolefins were investigated by a variety of techniques. Near room temperature PIB was found to be miscible with a limited range of polyolefin structures. The interactions for several blends in this range were determined by small-angle neutron scattering. The Flory-Huggins parameter x was found to be large and negative at room temperature in all cases, contrary to expectations and to previous experience with blends of other saturated ...

Research paper thumbnail of Crystallization Kinetics and Microdomain Structures for Blends of Amorphous-Crystalline Block Copolymers with Amorphous Homopolymers

Springer eBooks, 1994

Blends of a symmetrical diblock poly(ethylene-b-propylene) (DEP) and an atactic polypropylene (AP... more Blends of a symmetrical diblock poly(ethylene-b-propylene) (DEP) and an atactic polypropylene (APP) were studied by calorimetry, small angle neutron scattering, and electron microscopy. Addition of APP to DEP drastically changed the crystallization kinetics of the polyethylene block. The results were interpreted on the basis of the morphological studies of the microdomain structure in both the crystalline state and the melt state of the blends.

Research paper thumbnail of Compatibility and morphology of blends of isotactic and atactic polypropylene

Journal of Materials Science, Feb 1, 1991

Research paper thumbnail of Short Communication: Three Selected as PMSE Fellows in 2004

Polymer News, May 1, 2004

... in 2004 David J. Lohse ExxonMobil Research and Engineering Co. ... Nikos Hadjichristidis Bill... more ... in 2004 David J. Lohse ExxonMobil Research and Engineering Co. ... Nikos Hadjichristidis Bill MacKnight Don Schulz They were inducted as the fifth class of PMSE Fellows during the Awards Lunch at the Anaheim ACS Meeting on Monday, March 29th, 2004. ...

Research paper thumbnail of The configurational statistics of a polymeric chain confined by impenetrable barriers. II. The floating chain

Journal of Chemical Physics, Apr 15, 1977

ABSTRACT

Research paper thumbnail of Short Chain Branching Effect on the Cloud-Point Pressures of Ethylene Copolymers in Subcritical and Supercritical Propane

Macromolecules, Mar 26, 1998

Research paper thumbnail of Interfacial Aspects of Multicomponent Polymer Materials

Research paper thumbnail of Polymeric Compatibilizers: Uses and Benefits in Polymer Blends

Research paper thumbnail of Dynamic viscoelastic properties of poly(ethylene-propylene) diblock copolymer in the melt state and solutions

Research paper thumbnail of Structure Characterization in the Science and Technology of Elastomers

Publisher Summary This chapter discusses structure characterization in the science and technology... more Publisher Summary This chapter discusses structure characterization in the science and technology of elastomers. The chemical elemental analysis of polymers can often be carried out by the methods used for low-molecular-weight organic compounds. This is particularly true when combustion of the sample is involved. Thus, C, H, and N can be determined on milligram samples by complete combustion followed by gas chromatographie analysis of the gases evolved. Accuracy is about 0.3%. Quite often the composition of an elastomer is only an average of a wide distribution of structures. It can be a composite of polymer, additives, and impurities, and if the polymer itself contains more than one type of monomer unit, a variety of polymer compositions are possible. These can be distributed inter- and intramolecularly.

Research paper thumbnail of Graft Copolymers

Encyclopedia of Polymer Science and Technology, 2010