Semicrystalline block copolymers containing one crystalline block, such as PCL, show more complicated morphologies than amorphous block copolymers. This is because the microstructure of semicrystalline block copolymers is determined by the interplay between the microphase-separation temperature, crystallization temperature, and glass transition temperatures of the respective blocks. This paper describes initial results of thermodynamic and kinetic effects associated with microphase separation and crystallization in as-cast semicrystalline (PS)0.62(PCL)0.38, (PB)0.2(PCL)0.8 and (PS)0.35(PB)0.15(PCL)0.5 block copolymers, where the subscripts denote the mass fraction of each block.

Semicrystalline block copolymers (PS-b-PCL with Mn=209,000 g/mol, PB-b-PCL with Mn=146,000 g/mol and PS-b-PB-b-PCL with Mn= 150,000 g/mol) were prepared by anionic polymerization. Films were cast from 5% (mass fraction) solutions in toluene into ∼lmm thick films. A relatively slow solvent evaporation over approximately a 10 d period was achieved by partially covering the dishes containing polymer solutions.

Phase segregation is important in determining the properties of many complex polymers, including polyurethanes. Achieving a better understanding of the links between formulation, chemical nature of segregated phases, and physical properties, has the potential to aid development of improved polymers. However, the sub-micron size of segregated features precludes detailed chemical analysis by most existing methods. Zone-plate based, scanning transmission X-ray microscopes (STXM) at NSLS and ALS provide quantitative chemical analysis (speciation) of segregated polymer phases at ∼50 nm spatial resolution. Image sequences acquire much more data with less radiation damage, than spot spectra. After alignment, they provide high quality near edge spectra, and thus quantitative analysis, at full spatial resolution.

Fig. 1 shows an image and spectra acquired with the NSLS STXM of a macro-phase segregated TDI polyurethane. Spectral decomposition using model polymer spectra is used to measure the local urea, urethane and polyether content.

Despite the physical and technological significance of polymer interfaces (1), they have not been extensively studied using techniques based on electron scattering. Spontak et al. (2) used digital analysis of bright-field images to study Os-stained polystyrene-polydiene block copolymer interfaces, but work in this area has been lacking largely because of difficulties with staining or uncertainties in the distribution of stain at the nanometer length scales relevant to interfaces. Studies of polymer interfaces are now largely done by neutron scattering (3) This research explores the application of spatially-resolved electron energyloss spectroscopy to measure compositional widths of polymer-polymer interfaces. These first studies focus on blends of poly(2-vinyl pyridine) (PVP) dispersed in poly(styrene) (PS) to establish the various electron-optical, electron-scattering, and specimen-dependent limitations (4) to resolving such an interfacial width. The uncompatibilized PS/PVP interface should be relatively sharp.

Blends of PS (M.W. 190,000) and PVP ( M.W. 200,000) were made using a 5wt% solution of polymer in THF with a PS/PVP ratio of 7/3. The solution was cast into methanol. The resulting solid precipitate was removed and annealed under vacuum at 120°C for 36 hours.

Determination of internal structure of complex polymeric materials often requires a variety of analytical techniques. One technique that we have developed and recently employed for the first time for quantitative analysis is x-ray linear dichroism microscopy. With sensitivity to the presence and orientation of specific chemical functionalities within polymer molecules, x-ray linear dichroism microscopy provides a powerful tool to probe the internal structure of such molecules. We have used this ability to quantitatively analyze the lateral orientational order (tangential and radial orientation of transverse sections) within different grades of poly(p-phenylene terephthalamide) (Kevlar) fibers.

Kevlar fibers are highly crystalline and possess a complicated internal structure that exhibits lateral radial orientation. Figure 1 shows x-ray micrographs of (a) Kevlar 149, (b) Kevlar 49 and (c) Kevlar 29 fibers imaged at a photon energy specific to the aromatic functionality.

We are using the term "Industrial Polymers" to refer to polymers [plastics] that are produced by the ton or (in the case of films) by the mile. For example, in descending order of world-wide use (tonnage), the top eight of these polymers are polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), styrene polymers (including polystyrene - PS, and acrylonitrile-butadienestyrene/ styrene-acrylonitrile - ABS/SAN), polyesters (PETP), polyurethane (PU), phenolics and aminoplastics.

Industrial polymers, which have been produced by the millions of tons for the last five decades and are of obvious social and economic importance, have been exhaustively characterized. Structural features which affect physical properties and indicate process variables have been studied by many techniques other than microscopy (x-ray diffraction, thermal analysis, rheology, chromatographies, etc.). Microscopy techniques for polymer characterization have been well documented. Our motivation to apply field emission (high resolution) scanning electron microscopy to the study of polymers is: (1) The application of low voltage, high resolution SEM to biological materials is well characterized.

Superabsorbent polymers are often designed with increased density of crosslinking in the outer layer of the particles in order to improve liquid retention under load. For efficient product design, it is desirable to directly measure the spatial variation in crosslink density. Typically employed techniques (such as solvent uptake or measuring the changes in various mechanical properties such as the modulus) do not provide spatially resolved crosslink density information. We have applied Scanning Transmission X-ray Microscopy to examine the swelling of inhomogenously crosslinked superabsorbent polymers in deionized water and salt water solution.

Scanning Transmission X-ray Microscopy (STXM) is an effective way to study the chemical and morphological character of polymers on a sub micron spatial scale.1 STXM image contrast is based on core electron excitation by x-ray absorption; an interaction that has remarkable chemical sensitivity. Beam damage is less than in TEM microscopes and samples can be examined in wet and in ambient conditions.

Diblock copolymers consist of two chemically different polymer chains (or blocks) joined by a covalent bond. Because of the incompatibility between the two blocks and connectivity constraints, diblock copolymers spontaneously self-assemble into microphase-separated nanometer size domains that exhibit ordered morphologies at equilibrium. Commonly observed microdomain morphologies in bulk samples are periodic arrangements of lamellae, cylinders, and spheres. Recent studies show that the thin films of such block copolymers are of great potential for many nanoapplications including nanolithography and template synthesis for inorganic materials. Here, we report TEM studies of osmylated and ozonated thin diblock copolymer films.

An asymmetric block copolymer was synthesized with a composition of 36 kg/mol for the poly(styrene)(PS) block and 11 kg/mole for the poly (butadiene)(PB) block such that the microphase separation produces PB cylinders in a matrix of PS. The films were spin-coated from solution onto thin silicon nitride windows and annealed above the glass transition temperature in vacuum.

Polymer electrolytes are a topic of interest because of their potential applications in electrochemical devices. However, very few systems exhibit both high conductivities and mechanical strength. Composite polymer electrolytes, composed of conventional polymer electrolytes and inert fillers, provide an avenue to enhance mechanical strength while maintaining ionic conductivity, if the particle sizes of these inert fillers are sufficiently small (< 1 μm in diameter). The determination of the morphology for these inert fillers in polymer matrixes was undertaken to further our understanding of ion transport phenomena in these composite systems. This paper presents an in situobservation of inert fillers in liquid media using environmental TEM.

Surface-modified fume silica was prepared by a two-step process. (1) SiCl4 was used to activate surface silanol (SiOH) groups and generate reactive SiCl groups on the surface of fume silica particles (Aldrich, 7 nm in diameter).

Atomic force microscopy (AFM) was introduced in 1986 by Binnig, Quate and Gerber. In this method, a sample is scanned beneath a small, sharp silicon or silicon nitride probe attached to the apex of a flexible cantilever. Cantilever deflection is measured to give height information corresponding to the sample topography. Since AFM relies on tip-sample force interaction, the technique can be applied to insulators as well as to conducting and semiconducting materials. AFM therefore extends local probe studies to an important class of materials which can be difficult to investigate by electron microscopy and spectroscopy techniques owing to problems with sample charging. Among other materials, AFM has been used extensively to characterize the morphology, roughness, nanostructure, chain packing and conformation of polymer surfaces at the nanometer scale.

Early AFM studies of polymers were conducted in the contact mode and included the investigation of polymerized monolayers of n-(2-aminoethyl)-10,12-tricosadiynamide (AE-TDA) and poly(octadecylacrylate) (PODA) at submonolayer coverage.

Scanned-probe microscopy (SPM) has found application to a variety of polymer systems, primarily for the examination of surface morphology and the assessment of surface properties. In fact, SPM is unique in its ability to probe both phase morphology and mechanical properties simultaneously. The examination of industrial elastomers and their blends by SPM techniques can provide morphological information historically obtained only by transmission-electron microscopy (TEM). Since contrast with the SPM can be generated by differences in mechanical response of the constituent phases, polymer blends which are difficult to etch or stain for TEM can be successfully examined. In many cases measurements of polymer morphology can be made more easily with SPM, since time-consuming steps associated with thin-section production and staining are not required. Contact and tapping-mode operation along with force modulation and phase measurement can be used to examine phase microstructure, phase morphology, filler type, filler distribution, and viscoelastic response in elastomer systems.

Carboxylated latex has become very important in the formation of polymer films. In order to study the film and its properties it is important to know the morphology of the latex that is forming the film. The latex for this study has been examined by transmission electron microscopy(TEM) using positive preferential stains such as ruthenium tetroxide (RuO4) and cesium hydroxide(CsOH); and uranyl acetate(UAc) as a negative stain.

The polybutyl acrylate(PBA)/ polymethylmethacrylate(PMMA) composite latex particles consist of a soft core phase and a hard second phase with varying amounts of acrylic acid in the core, the shell and in both core and shell. The latexes were examined before and after cleaning. The cleaning was necessary in order to remove the surfactant and any small particles that might have formed during the emulsion polymerization. Prior to cleaning, the small particles adhered to the surfaces of the particles making it difficult to determine the final morphology of the latex particles.

The study of wetting and dewetting in thin polymer films has many implications for technological applications of polymer films, including dielectric films to control conductivity and colloidal paint systems. We have started to use a novel approach, Near Edge X-ray Absorption Fine Structure (NEXAFS) microscopy, to characterize dewetting in thin polymer films. We have investigated a polystyrene/brominated polystyrene (PS/PBrS) bilayer model system with the Scanning Transmission X-ray Microscope (STXM) at the National Synchrotron Light Source. Our method offers quantitative thickness mapping of all constituent components in these thin polymer films.

NEXAFS imaging of polymers has advantages over other forms of microscopy primarily because of its low damage, good chemical sensitivity, and the possibility for quantitative analysis. Figure 1 shows four micrographs of one PS/PBrS bilayer annealed for one week at 170 C.

In this work we apply the Hayashi-Nishi method for quantitatively analyzing the state of mixing of a secondary component in a polymeric matrix. We (1) evaluate the method using computer-generated morphologies and (2) compare the state of mixing of a core-shell impact modifier in polymers having differing affinity for the impact modifier. In the Hayashi-Nishi method two numbers, related to dispersion and distribution, are required to quantify the state of mixing of a secondary phase in a polymeric matrix. The 5-parameter in the Hayashi-Nishi method is defined as

The Ai's are the areas of each individual secondary phase particle or aggregate and nis the number of such particles in the image. S is related to the size distribution of these aggregate areas and is a measure of dispersion of the secondary phase in that particular image.

Silicone materials may be incorporated into organic thermoplastic resins to provide enhanced properties. Good dispersion of silicone with plastics is believed to be one of the keys to control the applications of these multiphase blends. In this study, we investigated the morphologies of mechanically mixed silicone/organic blends using scanning electron microscopy (SEM). Results provide an important piece of information that the optimum silicone phase dispersion can be achieved by matching the viscosities of the blend components.

Most silicone and organic polymers are thermodynamically immiscible, forming multiphase structures for their blends. For example, a blend consisting of 90 wt% polydimethylsiloxane (PDMS) and 10% low density polyethylene (LDPE) was revealed by SEM to have a multiphase structure shown in Figure 1A where the PDMS was a Dow Corning® 3-5016 silanol-terminated siloxane fluid that forms the dispersed phase and the LDPE a Dow Chemical polyethylene having a melt index of 4.

Plant fibers such as cotton, hemp and flax have been cultivated for textile purposes for thousands of years. These natural fibers play an important role in daily life as apparel fibers since they provide unique comfort properties unsurpassed by synthetic fibers. However, their use is not limited to the apparel sector. In recent years the market share of consumer textiles and industrial products made from all kinds of natural fibers has tremendously increased as they present a valuable source of renewable raw materials. Investigating their surface features by microscopic techniques is important to control the performance of the desired end-product. Processing steps involving heat, light or exposure to chemicals might have a significant impact on the specific surface properties of a fiber whether or not this was originally intended. Scanning electron microscopy is therefore a very useful tool for the characterization of textile products to determine the effectiveness and eventual resulting damage from physical or chemical treatments.

Natural fibers generally lack uniformity and large numbers of measurements often must be obtained to achieve estimates of sample parameters having reasonable levels of precision and confidence. This problem calls for automating the measurement and data analysis processes so obtaining a large amount of data is practical. We will discuss hardware and software designs used in our laboratory to automate microscope measurements and data analysis for fibrous materials.

Automating the measuring process requires constructing hardware to accomplish several tasks. Hardware should accommodate large-sized samples when they lack uniformity since many measurements are desirable. Sample positioning should be automated to remove the operator from the data acquisition process and eliminate a source of operator-dependent positioning error. Lens focusing should be automated since it is difficult to maintain flatness for large samples and the thickness of many samples exceeds the depth-of-focus of lenses. Finally, the quality of illumination provided to all sample locations during measurement should be flexible and consistent.

Single fiber fracture is important in understanding the fundamental failure mechanisms in wood/polymer composite products such as medium density fiberboard (MDF). The mechanical properties and fracture behavior of individual wood fibers has only recently been observable using a combination of environmental scanning electron microscopy (ESEM), laser scanning confocal microscopy and digital image correlation (DIC). Previous work has shown that specific areas on the fiber such as microcompressions and pits acted as crack nucelators and induce a brash fracture across the surface of the fiber. Given the development of these procedures it is now possible to observe and measure the mechanical properties and fracture characteristics of the wood fiber/ polymer composite fibers.

Individual black spruce wood fibers were coated with diphenylmethane 4-4'diisocyanate resin containing Hostasol Red GG. The addition of the Hostasol Red flurochrome provided the option of quantifying resin coverage by fluorescence microscopy.

Cotton is the single most economically important natural textile fiber in the world. It is a seed hair and has historically composed a large portion of the world's textiles. The plant is grown in most tropical and subtropical regions of the world. The demand for cotton, especially as a garment fiber, it due to properties such as its soft hand, water absorption, spinnability, and dyeability, and to its ease of home laundering. Perhaps cotton's most important textile property is its comfort. These properties are due to the unique, multilayered construction of the fiber subunits. The nature of this construction has been studied microscopically for more than 100 years, first using light microscopes, then electron microscopes as they became available. Because they are natural biological materials, no two cotton fibers are exactly alike. Yet they do have certain structural features in common. Structure in cotton can refer to several levels of construction.

Microscopical procedures for the evaluation of cotton textiles are important to the textile industry in evaluating mixed fiber blends, dyes and chemical finishes on fabrics. A new procedure for embedding cellulosic textiles has been developed for FT-IR microscopy whereby fibers are embedded in polystyrene. This polymer does not absorb in the same regions of the infrared spectrum as cellulose or traditional acrylate and epoxy resins that contain chemical groups in common with cellulose. Additionally, use of cross-sections mounted on a KBr disk (Fig. 1) has the advantage of better resolution (Fig. 2B) than grinding and pressing fibers in a KBr disk (Fig. 2A).

A new process for the evaluation of yarns has been developed. Approximately 2000 fibers before spinning, 50 yarn segments after spinning, or yarns removed from fabric after processing, can be encased in a tube, embedded in methacrylate plastic, quickly UV polymerized, and sectioned.

Multiple microspectroscopic imaging techniques have been employed to reveal the chemical and structural nature of flax (Linum usitatissimum L.) stem tissue, with the goal of finding the best technique by which to monitor retting processes for the production of linen fibers. Three of these techniques, which we have investigated for this purpose, are: mid-infrared (MIR), Raman and nuclear magnetic resonance (NMR) imaging. Initially, all three techniques were evaluated on the basis of their ability to reveal the nature of unretted flax stems. MIR imaging was found to be the most useful for this purpose. Thus, it was selected as the method of choice to follow retting processes to obtain flax fibers.

A Fourier transform (FT)-IR spectrometer equipped with microscope was used to acquire the MTR images. A FT-Raman spectrometer that was equipped with a Raman microprobe and utilizing a 1064 nm laser source was used to collect the Raman images.