Polymer/layered silicate nanocomposites: a review from preparation to processing

Foreign body reaction to biomaterials.

s, and 360 patents, and edited 12 books. He has also received over 80 major awards including the Gairdner Foundation International Award, Lemelson-MIT prize, ACS’s Applied Polymer Science and Polymer Chemistry Awards, AICHE’s Professional Progress, Bioengineering, Walker and Stine Materials Science and Engineering Awards. In 1989, Dr. Langer was elected to the Institute of Medicine of the National Academy of Sciences, and in 1992 he was elected to both the National Academy of Engineering and the National Academy of Sciences. He is the only active member of all three National Academies. Kevin Shakesheff was born in Ashington, Northumberland, U.K., in 1969. He received his Bacheclor of Pharmacy degree from the University of Nottingham in 1991 and a Ph.D. from the same institution in 1995. In 1996 he became a NATO Postdoctoral Fellow at MIT, Department of Chemical Engineering. He is currently an EPSRC Advanced Fellow at the School of Pharmaceutical Sciences, The University of Nottingham. His research group investigates new methods of engineering polymer surfaces and the application of these engineered materials in drug delivery and tissue engineering. 3182 Chemical Reviews, 1999, Vol. 99, No. 11 Uhrich et al.

Polymeric Systems for Controlled Drug Release

Nature’s hierarchical materials

Thermal conductivity of carbon nanotubes and their polymer nanocomposites: A review

Ethylene-octene copolymers prepared by Dow's INSITE™ constrained geometry catalyst technology present a broad range of solid-state structures from highly crystalline, lamellar morphologies to the granular morphology of low crystallinity copolymers. As the comonomer content increases, the accompanying tensile behavior changes from necking and cold drawing typical of a semicrystalline thermoplastic to uniform drawing and high recovery characteristic of an elastomer. Although changes in morphological features and tensile properties occur gradually with increasing comonomer content, the combined body of observations from melting behavior, morphology, dynamic mechanical response, yielding, and large-scale deformation suggest a classification scheme with four distinct categories. Materials with densities higher than 0.93 g/cc, type IV, exhibit a lamellar morphology with well-developed spherulitic superstructure. Type III polymers with densities between 0.93 and 0.91 g/cc have thinner lamellae and smaller spherulites. Type II materials with densities between 0.91 and 0.89 g/cc have a mixed morphology of small lamellae and bundled crystals. These materials can form very small spherulites. Type I copolymers with densities less than 0.89 g/cc have no lamellae or spherulites. Fringed micellar or bundled crystals are inferred from the low degree of crystallinity, the low melting temperature, and the granular, nonlamellar morphology. © 1996 John Wiley & Sons, Inc.

Classification of homogeneous ethylene‐octene copolymers based on comonomer content

Foreign‐body giant cells and polyurethane biostability: In vivo correlation of cell adhesion and surface cracking

Aging of poly(lactide)/poly(ethylene glycol) blends. Part 2. Poly(lactide) with high stereoregularity

Crystallization and phase separation in blends of high stereoregular poly(lactide) with poly(ethylene glycol)

Modified segmented polyurethanes were examined for biostability and biocompatibility using an in vivo cage implant system for time intervals of 1, 2, 3, 5, and 10 weeks. Two types of materials were used: polyether polyurethanes and polycarbonate polyurethanes. Two unmodified polyether polyurethanes (PEUU A' and SPU-PRM), one PDMS endcapped polyether polyurethane (SPU-S), and two polycarbonate polyurethanes (SPU-PCU and SPU-C) were investigated in this study. Techniques used to characterize untreated materials were dynamic water contact angle, stress-strain analysis, and gel permeation chromatography. Cellular response was measured by exudate analysis and by macrophage and foreign body giant cell (FBGC) densities. Material characterization, postimplantation, was done by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) in order to quantify biodegradation and scanning electron microscopy (SEM) to qualitatively describe the cellular response and biodegradation. The exudate analysis showed that the acute and chronic inflammatory responses for all materials were similar. Lower FBGC densities and cell coverage on SPU-S were attributed to the hydrophobic surface provided by the PDMS endgroups. The polycarbonate polyurethanes did not show any significant differences in cell coverage or FBGC densities even though the macrophage densities were slightly lower compared to polyether polyurethanes. By 10 weeks, biodegradation in the case of PEUU A' and SPU-PRM was extensive as compared to SPU-S because the PDMS endcaps of SPU-S provided a shield against the oxygen radicals secreted by macrophages and FBGCs and lowered the rate of biodegradation. In the case of polycarbonate polyurethanes, the oxidative stability of the carbonate linkage lowered the rate of biodegradation tremendously as compared to the polyether polyurethanes (including SPU-S). The minor amount of biodegradation seen in polycarbonate polyurethanes at 10 weeks was attributed to hydrolysis of the carbonate linkage.

A. Hiltner

Papers

Classification of homogeneous ethylene‐octene copolymers based on comonomer content

Foreign‐body giant cells and polyurethane biostability: In vivo correlation of cell adhesion and surface cracking

Aging of poly(lactide)/poly(ethylene glycol) blends. Part 2. Poly(lactide) with high stereoregularity

Crystallization and phase separation in blends of high stereoregular poly(lactide) with poly(ethylene glycol)

In vivo biocompatibility and biostability of modified polyurethanes