Papers by Elizabeth Orlowski
Rubber Chemistry and Technology, Sep 1, 2010
Linear triblock poly(styrene-b-isobutylene-b-styrene) (SIBS), the first representative of polyiso... more Linear triblock poly(styrene-b-isobutylene-b-styrene) (SIBS), the first representative of polyisobutylene (PIB)-based biomaterials, is approved by the Food and Drug Administration for use in the Taxus® Drug Eluting stent. SIBS and the new generation of dendritic or arborescent D_SIBS are self-assembling thermoplastic elastomers (TPEs), or “biorubbers.” D_SIBS has lower creep and improved fatigue life. We recently produced composites of novel D_PIB-based TPEs with carbon and silica. These composites had 2–10 times higher tensile strength than that of the neat polymer. The composite with 37.5 wt. % carbon black was nonconductive, demonstrating excellent filler dispersion. Transmission electron microscopy and atomic force microscopy analysis supported the formation of a nanocomposite with nanosized surface topology. The water contact angle of the biorubbers was significantly lower than that of silicone rubber. The carbon nanocomposite showed excellent biocompatibility in vivo, having thinner capsules than silicone after 180 days implantation into rabbits. Bone compatibility was also excellent. The improved biocompatibility was most likely due to a combination of hydrophilicity and surface nanotopology. Fundamental studies of the effect of surface properties of these biorubbers on biocompatibility are ongoing in our laboratory.
PJCT, 2012
Influence of e-beam irradiation on the chemical and crystal structure of poly(aliphatic/aromatic-... more Influence of e-beam irradiation on the chemical and crystal structure of poly(aliphatic/aromatic-ester) multiblock thermoplastic elastomers Poly(aliphatic/aromatic-ester) (PED) multiblock copolymers belong to the class of thermoplastic elastomers (TPEs), characterized by a physical network of semi-crystalline hard segments. The PEDs were modified with e-beam to create an additional network structure. Polymers were evaluated using SEC, WAXS, DSC and quasi-static tensile tests. E-beam irradiation induced a significant increase of molecular weight and tensile strength of the PEDs. This effect, together with the diminished degree of crystallinity can be explained by the formation of chemical crosslinks, which are located in the hard phase segments.
Rubber Chemistry and Technology, 2009
The tensile and thermal properties of linear poly(styrene-b-isobutylene-b-styrene) (L_SIBS) and s... more The tensile and thermal properties of linear poly(styrene-b-isobutylene-b-styrene) (L_SIBS) and styrenic copolymers with a dendritic polyisobutylene core (D_SIBS) filled with 10 – 30 wt% of organophilic montmorillonite nanoclays (Cloisite(®)-20A) via solution blending were investigated. D_SIBS polymers were successfully reinforced by the clays without additional compatibilizers to show increase in both modulus and ultimate tensile strength. The clay platelets were well dispersed in the polymer matrix as determined by transmission electron microscopy (TEM). However, L_SIBS composites displayed decreasing tensile strength with increasing clay loading. TEM found clay agglomerates in L_SIBS composites that can act as “hotspots” for premature failure of the material. D_SIBSs loaded with 60 phr (37.5 wt%) carbon black (N234) also showed significant reinforcement. Interestingly, a D_SIBS with 17 wt% hard phase content reinforced with 60 phr carbon black exhibited an increase in the glass t...
Rubber Chemistry and Technology, 2010
Linear triblock poly(styrene-b-isobutylene-b-styrene) (SIBS), the first representative of polyiso... more Linear triblock poly(styrene-b-isobutylene-b-styrene) (SIBS), the first representative of polyisobutylene (PIB)-based biomaterials, is approved by the Food and Drug Administration for use in the Taxus® Drug Eluting stent. SIBS and the new generation of dendritic or arborescent D_SIBS are self-assembling thermoplastic elastomers (TPEs), or “biorubbers.” D_SIBS has lower creep and improved fatigue life. We recently produced composites of novel D_PIB-based TPEs with carbon and silica. These composites had 2–10 times higher tensile strength than that of the neat polymer. The composite with 37.5 wt. % carbon black was nonconductive, demonstrating excellent filler dispersion. Transmission electron microscopy and atomic force microscopy analysis supported the formation of a nanocomposite with nanosized surface topology. The water contact angle of the biorubbers was significantly lower than that of silicone rubber. The carbon nanocomposite showed excellent biocompatibility in vivo, having t...
Macromolecular Symposia, 2008
Summary: This paper discusses the analysis of star‐branched and dendritic polyisobutylenes (PIBs)... more Summary: This paper discusses the analysis of star‐branched and dendritic polyisobutylenes (PIBs) using branching parameters based on radii of gyration Rg,z and hydrodynamic radii Rh,z. Rg,z and Rh,z were measured by Size Exclusion Chromatography equipped with a Wyatt Technology Viscostar viscometer (VIS), a Wyatt Optilab DSP RI detector, a Wyatt DAWN EOS 18 angle Multiangle Light Scattering (MALS) detector and a Wyatt Quasi‐elastic Light Scattering QELS detector. Branching parameters were calculated from these measurements and compared with those computed for these architectures.
Journal of Polymer Science Part A: Polymer Chemistry, 2007
The synthesis of the novel inimer (initiator‐monomer) 4‐(1,2‐oxirane‐isopropyl)styrene EPOIM and ... more The synthesis of the novel inimer (initiator‐monomer) 4‐(1,2‐oxirane‐isopropyl)styrene EPOIM and the copolymerization of this inimer with isobutylene (IB) to form arborescent polyisobutylene (PIB) is described. Polymerizations were accomplished by use of TiCl4 coinitiator and the effect of reaction conditions was investigated. Size exclusion chromatography (SEC) was used demonstrate EPOIM incorporation across the whole molecular weight distribution. The average number of branch points (B) per chain measured by use of selective link destruction increased with increasing EPOIM/IB ratio and decreased with [TiCl4]. Large scale polymerizations were carried out based on results from small scale polymerizations. Architecture analysis carried out through use of branching parameters based on the radii of gyration Rg and hydrodynamic radii Rh measured by multidetector SEC corroborated the proposed arborescent architecture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5847...
Biomaterials, 2010
This paper presents the synthesis and characterization of a polyisobutylene (PIB)-based nanostruc... more This paper presents the synthesis and characterization of a polyisobutylene (PIB)-based nanostructured carbon-reinforced thermoplastic elastomer. This thermoplastic elastomer is based on a self-assembling block copolymer having a branched PIB core carrying –OH functional groups at each branch point, flanked by blocks of poly(isobutylene-co-para-methylstyrene). The block copolymer has thermolabile physical crosslinks and can be processed as a plastic, yet retains its
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Papers by Elizabeth Orlowski