| Polymers Main Page > Research Highlights (Archives) |
| Back to Current Research Highlights |
Research Highlights of Polymers Division (Archives) |
Research highlights at the Year of 2003 |
A Fully Automated Peak Picking and Integration Algorithm for Mass Spectral Data |
| A numerical algorithm is described that accurately locates and calculates the area beneath peaks from real mass spectral data using only reproducible mathematical operations and no user-selected parameters. Such a fully automated algorithm was required for rapid and repeatable processing of mass spectral data containing hundreds of peaks. By working without any user input it both saves operator time and eliminates operator bias. The first criterion is desirable when processing large amounts of data (for example in proteomics research). The second criterion is necessary to the Polymer Division's goal of creating an absolute molecular mass distribution synthetic polymer Standard Reference Material where operator bias in the data analysis cannot be tolerated. |
Pore Size Distributions in Low-k Dielectric Thin Films from SANS Porosimetry |
| The microelectronics industry is testing a wide variety of porous low-dielectric constant ("low-k") materials for future use in integrated circuits. To understand low-k thin film properties, a quantitative analysis of pore size distribution is vital. The Electronics Materials group has developed a new approach to this challenging problem based on a small angle neutron scattering (SANS) porosimetry technique. The new technique quantifies pore size distribution and reveals subtle material characteristics inaccessible to other measurement techniques. |
Critical Dimension Metrology of Nanoscale Structures with Small Angle X-ray Scattering |
| The continued reduction in pattern sizes throughout the semiconductor industry will soon require new metrologies capable of high throughput non-destructive measurements of dense, high aspect ratio patterns with subnanometer resolution. In collaboration with industrial partners, we are developing a metrology based on Small Angle X-ray Scattering (SAXS) to quickly, quantitatively, and non-destructively measure the smallest, or "critical", dimensions expected in the next two technology nodes with subnanometer precision. Quantities of interest include critical dimension, pattern sidewall angle, statistical deviations across large areas, and quantitative measures of pattern sidewall roughness. These efforts are driving toward the specification of a laboratory scale device capable of providing pattern dimensions during routine tests of fabrication processes. |
| High-throughput Measurements of Elastic Moduli of Polymer Thin Films |
| As technology continues to strive towards smaller, thinner, and lighter devices, more stringent demands are being placed on polymer films as diffusion barriers, dielectric coatings, electronic packaging, etc. The material properties of thin films can be drastically different from that of the bulk material. Therefore, there is a growing need for testing platforms that allow for rapid determination of the mechanical properties of thin polymer films/coatings. We demonstrate here a novel measurement technique that yields the elastic modulus of supported polymer films in a rapid and quantitative manner without the need for expensive equipment or material-specific modeling. |
Elastic Flow Instability in Polymer-Dispersed Carbon Nano-tubes |
| Novel composites engineered from polymers and carbon nanotubes offer the promise of plastics with enhanced thermal, electronic, and mechanical properties, but the ability to control and quantify particle dispersion in such materials is an unresolved issue of fundamental importance. Of particular interest is how processing flows influence tube dispersion and orientation. We are developing metrologies and methods that directly address the fundamental nature of elastic flow instabilities in polymer-dispersed carbon nanotubes, enabling better control of dispersion during flow processing of melts and suspensions. |
Scaffold Structure and Cell Function Through Multi-modal Imaging and Quantitative Visualization |
| Non-destructive, in vitro evaluation of tissue engineered medical products (TEMPs) will shorten their development time. Imaging techniques such as collinear optical coherence and confocal fluorescence microscopies are being used to address the challenges of imaging these systems. An equally important component of the work is the image quantification as a vehicle to evaluate the voluminous imaging data. |
| |
Research highlights at the Year of 2002 |
Polyolefins |
Polyolefins: Serving the Largest Market |
| Polyolefins, primarily polyethylene and polypropylene, comprise the largest share of the U.S. market for polymers. Demand for the newer metallocene polyolefins is expected to grow 20 percent per year through 2006. The Polymers Division develops a variety of measurement tools and concepts to meet the broad needs of this diverse industry. Below, the program is broken down into four interrelated components: molecular characterization, microscopic structure, processing, and physical properties. Each component addresses the needs of different industrial segments, but together they provide a backbone for continued growth. While each component has focused on polyolefins, there is a broader applicability of the research. |
Micro-Confined Blends |
| Microscale processing is an emerging technology with unique challenges and applications in polymer processing and microfluidics industries, but the physics of processing emulsions when the drop size is comparable to a sample dimension is poorly understood. We are developing predictive models as we measure the effect of confinement and flow on the distribution and morphology of one component in another. |
Pore size distributions |
Pore size distributions in low-k dielectric thin films from X-ray porosimetry |
| NIST is working to provide the semiconductor industry with detailed information on the nanoscopic pore size distribution of porous thin films destined as low-k dielectric materials for the next generation of integrated circuits. The electronics industry has chosen the introduction of nanometer scale pores into interlayer dielectric films as the method of lowering the effective dielectric constant. While these modifications change the dielectric constant favorably, other important parameters such as physical strength and barrier properties will also change, often in an unfavorable way. A new method has been developed to calculate the pore size distribution from x-ray reflectivity measurements on thin films in a controlled environment of solvent vapor. |
Direct Measurement |
Direct Measurement of the Reaction Front in Chemically Amplified Photoresists |
| The continual device performance increases by the semiconductor industry has been largely driven by the fabrication of smaller structures with lithography. As feature sizes approach sub-100 nm, the photolithographic process must be controlled with tolerances of (2 to 5) nm, dimensions comparable to the molecular size of the polymer chains in the photoresist imaging material. New experimental methods are needed to measure transport and materials science phenomena over nanometer length scales to provide critically needed data for the understanding, design, and control of new lithographic materials and processes. In collaboration with IBM and the University of Texas, we directly measured the spatial evolution of a reaction front, within a photoresist, with nanometer resolution using neutron and x-ray reflectometry and a deuterium-labeled photoresist polymer. |
Metrologies for Tissue Engineering |
| Tissue engineering represents a new paradigm in medicine by seeking to regenerate missing or damaged tissue. Developing, manufacturing, and regulating tissue engineered medical products require proving the safety and efficacy of these complex devices. This presents a significant measurement challenge involving qualification of materials, cells, and delivery methods. |
NIST Combinatorial Methods Center |
| The NIST Combinatorial Methods Center (NCMC) was formally established in January 2002 to provide information and expertise on combinatorial methods to a wide range of industrial, academic and government institutions interested in acquiring combinatorial and high-throughput capabilities suited for materials research. The NCMC functions through two complimentary efforts. 1) A research program geared towards the development of techniques and instrumentation for the fabrication and analysis of novel combinatorial libraries. This research centers on novel gradient combi methods, where the NCMC has recognized expertise. 2) An outreach program designed to gauge industrial needs in combi research and effectively disseminate data, instrumentation design, best practices and protocols, and other information relevant to combi techniques. |
Research highlights at the Year of 2001 |
Composites Materials |
Off-Shore Oil Industry Benefits From New Tools for Design of Composite Structures |
| The off-shore oil industry needs the light weight of composite structures if it is to retrieve the vast supply of oil that exists in deep water deposits. In the last five years, fabricators have make composite components such as drilling and production risers, but their light weight can magnify problems such as harmful vibrations induced by waves and currents. A joint program between NIST and the University of Houston has provided the first tools that allow industry to simultaneously optimize material selection and structural design to control unwanted vibrations in drilling and production risers. The basic material property data are generated by NIST and used in a computer model developed by the University of Houston to predict vortex-induced vibrations so the effects of changes in material and design can be determined. |
Processing Temperature |
Fluorescence Based Temperature Measurements Impact Industrial Polymer Processing |
| Temperature is the most important parameter for controlling and modeling polymer processing. It plays a fundamental role in determining flow characteristics, degradation phenomenon, phase transitions, and morphology of the final product. Accurate measurements of resin temperature are not obtained using conventional methods such as thermocouples because such devices are unduly influenced by the large thermal mass of the processing machine. Resin and machine temperatures are never the same because the viscous resin dissipates energy during flow causing its temperature to increase significantly, sometimes approaching the degradation threshold. Our method to measure the true resin temperature is based on fluorescence spectroscopy. The technique has implications for materials testing, for development of processing strategies and for process control. |
Processing Sharkskin |
New tools in the battle against the “sharkskin” instability in polymer extrusion |
| The throughput of widely used polyolefins is limited by a processing defect known as “sharkskin,” which is a flow instability that causes an undesirable surface roughness on the extruded polymer. Polymer processing additives (PPAs) are commonly used to eliminate sharkskin, and hence are an enabling technology for the polyolefin industry. However, the mechanism by which they work is unclear, hindering development of next generation additives. We developed a capillary rheo-optics technique to visualize how PPAs eliminate sharkskin. We successfully monitored the coating of the PPA onto the internal surface of the capillary die wall and also measured extraordinary levels of slippage between the PPA and the polyolefin. These results provide the first quantitative measurement tools with which to gauge PPA performance. |
Reference Materials |
Polymer Reference Materials for Calibration of Instruments and for Benchmarking |
| Standard reference materials and reference materials are issued to address needs of the producers, processors and users of polymers for calibration and for performance evaluation of instruments used in the control of the synthesis and processing of polymers as well as benchmarks for comparisons of measurement methods and development of new materials. Recently produced standard reference materials include polyethylene of narrow mass distribution certified for mass average molecular mass and intrinsic viscosity and a nonlinear fluid standard for rheological measurements. In addition, the first reference biomaterial, an orthopedic grade ultrahigh molecular weight polyethylene, was issued for use in development of improved test methods for wear and as a benchmark for development of improved materials. 40 50 DRI Signal |
Dental Materials |
Nitric Acid-Modified N-Phenyliminodiacetic Acid – A Total Self-etching Primer for Bonding to Tooth Structure |
| Dental manufacturers and practicing dentists need stable, simplified, self-etching primers that will simultaneously condition both dentin and enamel surfaces and also mediate effective bonding to these mineralized tissues. Such self-etching primers will overcome many of the problems of current dental adhesives, promote conservative dentistry and benefit the general public. |
Combinatorial Methods |
Combinatorial Measurements of Phase Separation and Dewetting in Polymer Films |
| An understanding of the stability and homogeneity of thin polymer films on solid substrates has technological and scientific importance in applications ranging from coatings, dielectric layers, and lubricant surfaces to fundamental studies of polymer thin films. Dewetting and phase separation are two important and commonly occurring phenomena that can be used to control the morphology, topography and chemical composition heterogeneity of polymeric surfaces. These phenomena are influenced by a large number of factors that include both material properties as well as process variables, leading to a multidimensional parameter space that is difficult to explore by conventional experimental and analysis methods. The power of combinatorial methods for mapping out phase separation and dewetting in polymer thin films is demonstrated here. |
Low-k Dielectric Thin Films |
Structure and Property Measurements of Porous Low-k Dielectric Thin Films |
| Low-k interlayer dielectric materials have been identified by the microelectronics industry as a critical factor to enable deep submicron technology for the continued improvement of integrated circuits. NIST is working to provide the semiconductor industry with unique on-wafer measurements of the physical and structural properties of porous thin films important to their use as low-k dielectric materials. We have developed a novel methodology utilizing several complementary experimental techniques to measure the average pore size, porosity, pore connectivity, film thickness, matrix material density, coefficient of thermal expansion, moisture uptake, and film composition of several classes of candidate porous thin film materials. |
High speed electronics |
Polymer composite dielectrics enable development of embedded decoupling capacitance technology for high speed electronics |
| Increased signal speed within electronic circuits can be achieved by creating an efficient local power supply for charging fast processors and switching devices. Current technologies utilize surface mount discrete capacitors, which become ineffective at frequencies approaching 1 GHz. Our effort focused on embedded capacitance layers made of polymer composite films to effectively eliminate the switching noise. We have developed a specialized test vehicle design and invented a new testing procedure to verify the efficiency of embedded capacitance on circuit boards and to measure the broad-band dielectric permittivity of new materials at functional frequencies from 100 MHz to 10 GHz. |
| NIST Material Science & Engineering Laboratory - Polymers Division |
