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The surface chain conformations of poly(methyl methacrylate) (PMMA) at different temperatures were extensively studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Similar to our previous experimental studies on polystyrene (PS) and poly(2, 3, 4, 5, 6-pentafluorostyrene) (5FPS), a transition temperature ( T T ) could be identified through the principal component analysis (PCA) of the ToF-SIMS spectra obtained from the PMMA samples annealed at different temperatures. Interestingly, our results show that the T T depended on molecular weight and was about 50–60˚C below the bulk glass transition temperature ( T g ) and therefore could possibly be related to the surface glass transition temperature ( T g S ). These results were confirmed by contact angle measurements. ToF-SIMS results showed higher peak intensities of several low-mass oxygen-containing positive ions, hydrocarbon positive ions and OCH3− negative ion at higher temperatures, which can be interpreted by a higher surface concentration of methoxy groups at the surface.

Clean surface of graphene was obtained at 500 °C and characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the XPS C1s spectrum of graphene, besides an asymmetric sp2 carbon peak and a π-π∗ shake-up peak appeared, an additional sp3 carbon peak representing sp3 defects was also present. In the ToF-SIMS positive ion spectrum of graphene, a series of CxH2+ ions originated from the defects of graphene was found. To determine the origin of the CxH2+ ions, defects were created on the surface of nearly defect-free highly oriented pyrolytic graphite (HOPG) by bombarding it with a Cs+ ion beam at various sputtering doses. A detailed examination of the positive ion spectra of ion-bombarded HOPG surfaces reveals the presence of the CxH2+ ions, confirming that these CxH2+ ions, which came from the defects created on the sputtered HOPG surfaces, are similar to the defects present on graphene surface. A sp3 carbon peak at 285.3 eV, representing sp3 defects appeared in the XPS spectra of sputtered HOPG samples, confirms that the surface of the sputtered HOPG is similar to that of graphene. Fragmentation mechanisms of selected ions in the ToF-SIMS spectra of graphene and HOPG were proposed.

Polydimethylsiloxane (PDMS)-grafted nanoparticles and PDMS were added, respectively, to inhibit the dewetting of polymer films and the formation of surface patterns in spin coating. Uniform and flat films were successfully achieved with the addition of PDMS-grafted silica nanoparticles or PDMS. Time-of-flight secondary ion mass spectrometry depth profiling indicated that PDMS-grafted silica nanoparticles and PDMS preferentially segregated to the surface. A high concentration of bromine end groups was observed at the interface. The surface layer of PDMS or PDMS-grafted silica nanoparticles can decrease the surface tension of the polymer solutions and reduce the evaporation rates of the solvents, providing more time for the bromine end groups to anchor themselves at the silicon substrates. Copyright © 2016 John Wiley & Sons, Ltd.

Hydrogenated graphite powder was obtained through Birch reduction of graphite powder and characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) at 500 °C. The sp3 carbons formed at the edges of the surface of the hydrogenated graphite powder exhibited an sp3 carbon peak in the XPS C1s spectrum. The sp3-to-sp2 carbon ratio calculated from the XPS spectra increased from 0.08 to 1.19 after hydrogenation. Two sets of peaks, the Cx− and CxH− ion series (where x = 1, 2, 3…), were identified in the ToF-SIMS spectra of both the graphite powder and hydrogenated graphite powder. The difference between these two spectra represented an increase in the normalized intensities of the H− and CxH− ions in the spectrum of the hydrogenated graphite powder, indicating the formation of more sp3 carbons on the surface.

The cleanliness of the surface of graphene is important for its proper functioning in devices and sensors. Impurities including residual poly(methyl methacrylate) (PMMA) and hydrocarbon contaminants can alter its electronic and chemical properties. In this study, we used two surface-sensitive techniques, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), to monitor the chemical composition of the surface of graphene after washing it with acetone and annealing at high temperatures. The concentration of residual PMMA and hydrocarbon contaminants decreased as the annealing temperature increased. The atomic ratio of sp3 carbons to sp2 carbons of a clean graphene surface determined using XPS can be used to estimate the amounts of sp3 defects in graphene. ToF-SIMS spectra indicate that residual PMMA was removed from the surface of graphene at 400 °C, while hydrocarbon contaminants required a higher temperature of 500 °C to remove. In ToF-SIMS spectra obtained at 500 °C, the characteristic ions for graphene, which are related to cleavage of ring structure, include Cx+ (x = 1, 2, 3…), CxH+ and CxH2+ as well as Cx− and CxH−. For the first time, we developed a process to produce a very clean graphene surface which was verified by ToF-SIMS and XPS analyses.

Poly (2, 3, 4, 5, 6-pentafluorostyrene) (5FPS) was prepared by bulk radical polymerization. The spin-cast films of this polymer were analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) at various temperatures ranging from room temperature to 120°C. Principal component analysis (PCA) of the ToF-SIMS data revealed a transition temperature (T(T)) at which the surface structure of 5FPS was rearranged. A comparison between the results of the PCA of ToF-SIMS spectra obtained on 5FPS and polystyrene (PS) indicate that the pendant groups of 5FPS and PS moved in exactly opposite directions as the temperature increased. More pendant groups of 5FPS and PS migrated from the bulk to the surface and verse versa, respectively, as the temperature increased. These results clearly support the view that the abrupt changes in the normalized principal component 1 value was caused by the surface reorientation of the polymers and not by a change in the ion fragmentation mechanism at temperatures above the T(T). Contact angle measurement, which is another extremely surface sensitive technique, was used to monitor the change in the surface tension as a function of temperature. A clear T(T) was determined by the contact angle measurements. The T(T) values determined by contact angle measurements and ToF-SIMS were very similar.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra of polystyrene (PS) films supported on silicon wafers were obtained at temperatures ranging from room temperature to 100 °C. Principal component analysis (PCA) of the TOF-SIMS data revealed a transition temperature (TT) at which the surface structure of PS was rearranged. The TT of a 120-nm thick PS (weight-average molecular weight of 3,000 g/mol) thin film was determined to be about 36 °C, which is approximately 30 °C lower than the bulk glass transition temperature (Tg) of that PS. Similar TTs were observed on PSs with different molecular weights. As the TT is strongly related to the Tg and dependent on the molecular weight, it is believed that the TT determined by TOF-SIMS is related to the surface glass transition temperature (Tg(S)) measured by other techniques. This suggests that TOF-SIMS combined with PCA can be used to determine the Tg(S) of polymer films. Furthermore, the detailed PCA analyses indicate that the phenyl groups of PS tended to move away from the surface at temperatures above TT. This conclusion was further confirmed by contact angle and XPS measurements.

Stable and unstable spin-coated polymer films were prepared using various solvents and substrates. The relationship between polymer end-group concentrations and stability of spin-coated polymer films was revealed by time-of-flight secondary ion mass spectrometry depth profiling. A high concentration of bromine end groups at the interface between the polymer and the substrate helped to prevent the dewetting of films. In contrast, the bromine end groups were found to be more evenly distributed in unstable thin films. The extent to which the bromine end groups segregate to the interface depended on the competitive interactions between the polymer, the solvent and the substrate. Stronger polymer–solvent and solvent–substrate interactions prevented the segregation of the bromine end groups to the interface, resulting in unstable polymer films. Copyright © 2013 John Wiley & Sons, Ltd.

The effects of argon (Ar) and a mixture of Ar and oxgyen(Ar/O2) plasmas on amorphous and semi-crystalline poly(bisphenol A hexane ether) thin films were investigated by time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and principal component analysis (PCA). PCA results of the ToF-SIMS spectra indicate that an Ar/O2 plasma produced less physical sputtering and had a higher chemical reactivity than did an Ar plasma, regardless of whether an amorphous or a crystalline surface was involved. However, the chemical differences between the Ar- and Ar/O2-plasma-treated semi-crystalline films were much smaller. The observed results can be explained by the higher resistance of the polymer crystalline regions to physical sputtering and chemical etching. Copyright © 2013 John Wiley & Sons, Ltd.

Extended Abstract Graphene, a single layer of graphite, has attracted much attention due to its physical properties and two-dimensional structure. It has been used in many important industrial applications, including batteries, electronic devices and sensors. The cleanliness of graphene surfaces is important for successful uses of graphene in these applications. Surfaces of highly oriented pyrolytic graphite (HOPG), which can be regarded as the surfaces of defect-free graphene and surfaces of graphene were characterized by two very powerful surface analysis techniques X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) [1-4]. XPS results indicated that the impurities on the surfaces of graphene and HOPG can be removed by annealing samples of graphene and HOPG in vacuum at 400 o C [5]. In addition, ToF-SIMS results showed that even a small amount of poly(methyl methacrylate) (PMMA) impurity on the graphene surface can be removed by annealing the sample in vacuum at 500 o C. In the C1s spectrum of clean HOPG, an asymmetric sp 2 carbon peak and a π-π* shake-up peak were present, indicating the absence of defects. An additional sp 3

Surface patterns were observed on spin-coated poly(bisphenol A decane ether) (BA-C10) films prepared with chloroform and tetrahydrofuran as the solvents. The interior structure of these surface patterns were analyzed using a time-of-flight secondary ion mass spectrometry (ToF-SIMS) equipped with a bismuth cluster source for ion imaging and a C(60)(+) cluster source for depth profiling. For the first time, the surface patterns have been shown to be hollow rather than solid using ToF-SIMS three-dimensional (3D) analysis and optical techniques. Moreover, the microarea depth profiling analysis indicated that the hollow structure was sandwiched between two polymer layers rather than sitting on the substrate. The height of the hollow structure and the thicknesses of the polymer layers above and below the hollow structure were also estimated from the depth profiling results.

The thermal properties of the fluorocarbon–hydrocarbon copolymer [-(CF2)8-(CH2)10-]N were characterized using polarized optical microscopy, differential scanning calorimetry and X-ray diffraction. The results revealed the presence of a crystalline phase and a threaded nematic liquid crystal phase. The changes in the surface composition during annealing were studied in situ using time-of-flight secondary ion mass spectrometry. The spectra were interpreted using principal component analysis (PCA). The surface compositions at different thermal states can be distinguished by PCA. Moreover, a PCA loadings analysis revealed a continuous increase in the concentration of the hydrocarbon segments on the surface as the polymer gradually changed from the amorphous state to the liquid crystal state and finally the crystalline state. This suggests that the chemical composition of the surface in the amorphous state is controlled by the surface energy difference between the fluorocarbon and hydrocarbon segments, while the surface composition in the crystalline state is controlled by the structural ordering of the fluorocarbon segments. The results also showed that the surface re-construction of this polymer was highly reversible. Copyright © 2012 John Wiley & Sons, Ltd.

This report provides detailed experimental results of thermal and surface characterization on untreated and surface-treated halloysite nanotubes (HNTs) obtained from two geographic areas. Surface characterization techniques, including XPS and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used. ToF-SIMS surface analysis experiments were performed with both atomic and cluster ion beams. Higher ion yields and more high-mass ions were obtained with the cluster ion beams. Static ToF-SIMS spectra were analyzed with principal component analysis (PCA). Morphological diversities were observed in the samples although they mainly contained tubular structures. Thermogravimetric data indicated that aqueous hydrogen peroxide solution could remove inorganic salt impurities, such as alkali metal salts. The amount of grafting of benzalkonium chloride of HNT surface was determined by thermogravimetic analysis. PCA of ToF-SIMS spectra could distinguish the samples minedfrom different geographical locations as well as among surface-treatedand untreatedsamples. Copyright c � 2010 John Wiley & Sons, Ltd.

Poly(bisphenol-A-etheralkane), BA-Cn(n, which is the number of aliphatic CH2 units, = 8 and 10), composed of rigid and flexible segments, is a semicrystalline polymer. In 50-nm-thick films, the polymers tend to develop flat-on lamellae at the surfaces. Principal component analyses (PCAs) of the ion images were used to discriminate the conformation between the amorphous and flat-on lamellar surfaces of the polymers. The changes of the surface structure were directly detected by time-of-flight secondary ion mass spectrometry chemical imaging when flat-on lamellae were developed from the polymer melts. These structural changes were related to the lengths of the folded segments, which were strongly influenced by the crystallization temperature. The PCA loading analyses suggested that the length of the folded segments, which contained flexible and the rigid segments with an ether linkage, increased when the crystallization temperature decreased, suggesting the kinetic origin of polymer crystallization. Copyright © 2010 John Wiley & Sons, Ltd.

The effect of film thickness on the structural conformation of the surfaces of the amorphous state, edge-on lamellae and flat-on lamellae of a semiflexible polymer, poly(bisphenol-A-etheroctane), was investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS) with the aid of principal component analysis (PCA). PCA results empirically indicate that a structurally regular polymer surface was obtained with the formation of the flat-on lamellae from the amorphous state at a low degree of supercooling. A higher concentration of end group and cilium ion fragments, which are indicative of free chain ends, was observed on the edge-on lamellar surfaces than on the amorphous and the flat-on lamellar surfaces. This finding was attributed to the fact that the lateral surface of the edge-on lamellae contains many growth fronts, leaving behind a large number of uncrystallized chain remnants on the surfaces. Structural disorder was facilitated on both edge-on and flat-on lamellar surfaces as the film thickness decreased. Hence, this PCA study offers new insights into the nonequilibrium nature of polymer crystals and the mechanism of polymer crystallization in thin and ultrathin films.

In this article, we addressed the applicability of time-of-flight secondary ion mass spectrometry (TOF-SIMS) to examine the effects of molecular weight and of flexible-segment length on the polymer chain arrangement at the folding surfaces of the lamellae. Poly(bisphenol A-etheralkane) (Cn) contains both rigid aromatic and flexible aliphatic CH(2) segments. The number of CH(2) units per flexible segment, n, varies from 8 to 12. Principal component analysis (PCA) of TOF-SIMS data revealed the chemical and structural variations of the folding surfaces of these polymers and identified the ion peaks contributing to these variations. We highlighted the discriminating power of PCA to distinguish the structural conformations of the amorphous and flat-on lamellar surfaces of these polymers. PCA loadings analyses showed that relatively more flexible structures were deposited on the folding surfaces when the flexible-segment length increased from 8 to 10 CH(2) units. The concentration of short loops at folding surfaces and the disorder of folding surfaces increased when the molecular weight increased. All these results led us to conclude that TOF-SIMS has great potential for probing the chemical composition of the folding surfaces of polymers.

In this work, we examined the effects of the liquid crystalline ordering on the surfaces of thermotropic fluorocarbon-hydrocarbon polymers (FmHn, with m = 8; n = 8, 10) by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with principal component analysis (PCA). XPS results showed that the liquid crystal surfaces of the polymers were enriched with hydrocarbon segments. PCA of ToF-SIMS data further showed that reversible structural changes between the amorphous and ordered states of the polymers occurred. As these polymers ordered at room temperature, their surfaces were transformed from the amorphous state with fluorocarbon-segment enrichment to the fully ordered liquid crystal states with hydrocarbon-segment enrichment. All these results suggested that the molecular orientation controlled the surface composition of the liquid crystalline polymers notwithstanding the surface energy. The axial alignment of the rigid fluorocarbon mesogens anchored the flexible hydrocarbon segments at the surface. Copyright © 2010 John Wiley & Sons, Ltd.

We reveal that a beam of low-energy electrons (18 eV) can directly trigger long-range molecular ordering of an amorphous, semi-flexible oligomer in a few minutes without the prerequisite of pre-orientation. A strong endothermic transition was detected with a micro-thermal analyzer on the areas that had been exposed to the electron irradiation while the areas that were shielded from the irradiation by a protective mask remained amorphous as usual. This result suggests that long-range molecular ordering only develops in the area of the oligomer film under electron irradiation. This is the first-time effort to use electron irradiation to control the long-range ordering of an amorphous organic thin film above the glass transition temperature.

Small-angle X-ray scattering revealed that a semirigid oligomer of bisphenol-A-co-ether-octane with a monodisperse chain length is capable of forming ciliated-folded, once-folded, ciliated-extended and fully extended lamellar structures. Isothermal crystallization studies suggested a sequence of structures with increasing crystallization temperature, from a ciliated-folded to a once-folded form and then to a ciliated-extended form as the degree of supercooling is decreased. The crystal surface thus changed from octane cilia to bisphenol A segments and then back to octane cilia as the lamellar structure changed. The results of time-of-flight secondary ion mass spectrometry analyses strongly supported the fold structural models.

The fold and lateral surfaces of chain-folded lamellae of poly(bisphenol-A-co-etheroctane), containing both aliphatic CH 2 and aromatic segments, were investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). At low and high crystallization temperatures, the surfaces of the polymer films were shown to consist mainly of edge-on and flat-on lamellae, respectively. Surfaces with a mixture of edge-on and flat-on lamellae were produced at intermediate temperatures. The edge-on and flat-on lamellae were identified by using ions that recognize the flexible and rigid segments of the polymer. Ion images produced using selected ions that are related to the edge-on or flat-on orientation can be used to identify the location of these lamellae on the polymer surface. Our results indicate that ToF-SIMS can be used to detect different lamellar orientations at the surfaces of semi-crystalline polymers.

The dependence of the lamellar growth kinetics on the molecular weight (MW) of poly(bisphenol A octane ether) (BA-C8) in the low crystallization temperature region was investigated using atomic for...

[(BA-C8) 18 –(6FBA)] n was synthesized by condensation polymerization of poly(bisphenol A- co -octane) containing 18 repeat units with bromine end groups, (Br–(BA-C8) 18 –Br), and 4,4′-(hexafluoroisopropylidene)diphenol (6FBA). This copolymer was confirmed to be semicrystalline after a single melting temperature was detected by differential scanning calorimetry. The changes in the surface chemical composition were measured using time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy, the changes in the surface energy were measured using contact angle measurements, and the changes in the surface morphology were detected using atomic force microscopy as the copolymer crystallized. A decrease in the surface fluorine concentration with time was detected because of the movement of the low surface energy units (6FBA) to the bulk during the development of the crystalline phase. This result shows that the decrease in the enthalpy as a result of crystallization overcomes the increase in the surface free energy due to the migration of the low surface energy units to the bulk and the decrease in entropy due to demixing.

Poly(styrene) (PS), poly(2,3,4,5,6-pentafluorostyrene) (5FPS) and their random copolymers were prepared by bulk radical polymerization. The spin-cast polymer films of these polymers were analyzed using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The surface and bulk compositions of these copolymers were found to be same, implying that surface segregation did not occur. The detailed analysis of ToF-SIMS spectra indicated that the ion fragmentation mechanism is similar for both PS and 5FPS. ToF-SIMS quantitative analysis using absolute peak intensity showed that the SIMS intensities of positive styrene fragments, particularly C 7 H 7 + , in the copolymers are higher than the intensities expected from a linear combination of PS and 5FPS, while the SIMS intensities of positive pentafluorostyrene fragments are smaller than expected. These results indicated the presence of matrix effects in ion formation process. However, the quantitative approach using relative peak intensity showed that ion intensity ratios are linearly proportional to the copolymer mole ratio when the characteristic ions of PS and 5FPS are selected. This suggests that quantitative analysis is still possible in this copolymer system.

A poly(bisphenol A octane ether) (BA-C8) was synthesized. The isothermal spherulitic growth process was studied in situ using atomic force microscopy (AFM) at room temperature. For spherulites formed by homogeneous nucleation, the growth process includes the birth of a primary nucleus, the development of a founding lamella and the growth of the founding lamella into a spherulite. An embryo below a critical size is unstable. A stable embryo grows into a founding lamella. There is only one founding lamella in each spherulite. All other lamellae originate from this founding lamella. Two eyes can be seen at the center of a spherulite. For spherulites formed through heterogeneous nucleation, many lamellae grow at the nucleus surface and propagate outward radially. The spherulites acquire spherical symmetry at the early stage of crystallization. No eyes are found for this kind of spherulites.

The polymers BA-C8 and 6FBA-C8 were obtained by condensation polymerization of 1,8-dibromo-octane with bisphenol A and 4,4′-(hexafluoroisopropylidene)diphenol, respectively. A blend (BA-C8/6FBA-C8 (80/20)) containing 80 wt% of BA-C8 and 20 wt% 6FBA-C8 was prepared. Only one glass transition temperature was detected using a differential scanning calorimeter, suggesting that the blend is miscible. The surface chemical and morphological properties of the blend were studied as BA-C8 crystallized using atomic force microscopy, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and contact angle measurements. The results of the surface analyses showed that the surface of the blend was found to be enriched in the 6FBA-C8 polymer, especially at the crystalline regions. The crystalline regions were found to be raised above the amorphous regions. Surface segregation and crystallization were the two main factors that contributed to the changes in the chemical composition and morphology of the surface.

Fluorocarbon–hydrocarbon microblock copolymers –(CF2)n–(CH2)m– (n = 4, 6, 8; m = 6, 8, 10) were synthesized. Binding energies of the C 1s and F 1s peaks of these copolymers were measured using x-ray photoelectron spectroscopy. The binding energy of the C 1s peaks of the carbon atoms of the hydrocarbon segments was set at 285.0 eV as the binding energy reference. Unexpectedly, the binding energy of the C 1s peak corresponding to the CF2 group of the microblock copolymers was determined to be ∼291.4 eV, which is ∼0.8 eV lower than that of the CF2 group of tetrafluoroethylene. Copyright © 2003 John Wiley & Sons, Ltd.

A series of fluorinated polymers were studied using time-of-flight secondary ion mass spectrometry (ToF-SIMS) to investigate the relationship between the structures of the polymers and secondary ions. The influence of fluorocarbon segment length on the formation of secondary ions in a ToF-SIMS process was studied. The characteristic negative and positive ions were found to be related to the chemical structure of the repeat units of the polymers. The ToF-SIMS results provided some useful information on the fragmentation mechanism of positive and negative secondary ions. The results indicate that recombination of the ions in the gas phase is unlikely in a static SIMS process. Copyright © 2002 John Wiley & Sons, Ltd.

Two series of sequential polymers (6FBA–Cn and BA–Cn) have been synthesized by phase-transfer catalyzed polyetherification of 1,n-dibromoalkane (n=4,6,8,10,12,14 and 18) with 4,4′-(hexafluoroisopropylidene)diphenol (6FBA) and bisphenol A (BA). The effects of the flexible aliphatic segment length on the structure of secondary ions were investigated. The characteristic secondary positive and negative ions in the time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra are related to the chemical structures of the sequential BA–Cn and 6FBA–Cn polymers. The emission of the characteristic secondary positive and negative ions occurs after cleavage of the C–O bonds of the polymer repeat units. In the ToF-SIMS negative spectra, a series of small peaks separated by 14 amu provides the information about the flexible segment lengths of the repeat units of the BA–Cn and 6FBA–Cn polymers and can be used to directly determine the number of the –CH2– groups, n, of the flexible segment.

The dynamic growth processes of lamellae and spherulites of a polymer (BA-C8) synthesized by condensation polymerization of bisphenol A and 1,8-dibromooctane were directly observed using an atomic force microscope at 25 ± 1 °C. The phase shift measured at the tip of growing lamellae is lower than the phase shifts of the other regions of the lamellae. This result indicates that the growth front of a lamella is softer and contains more defects than the developed ones. The growth process of lamellae and the formation of spherulites were studied. A lamella was observed to breed more lamellae by inducing adjacent secondary nuclei and to develop into a lamellar sheaf and finally into a spherulite. The lamellae were preferentially oriented edge-on with respect to the surface of the BA-C8 polymer thin films. The detailed observations on the formation of the secondary nuclei indicated that the branching of the lamellae was only a temporary growth stage of the secondary lamellae. At the branch point, the secondary ...

Two series of sequential polymers were synthesized by polymerization of 1,n-dibromoalkane (n = 4, 6, 8, 10, 12, 14, and 18) with 4,4‘-(hexafluoroisopropylidene)diphenol (6FBA) and bisphenol A (BA)....

High-impact polystyrene (PS) nanocomposites filled with individually dispersed halloysite nanotubes (HNTs) were prepared by emulsion polymerization of styrene in the presence of HNTs with sodium dodecyl sulfate (SDS) as the emulsifier. The SDS is a good dispersing agent for HNTs in aqueous solution. The emulsion polymerization resulted in the formation of polystyrene nanospheres separating individual HNTs. Transmission electron microscopy revealed that the HNTs were uniformly dispersed in the PS matrix. Differential scanning calorimetry, Fourier-transform infrared spectroscopy and thermogravimetry were used to characterize the PS/HNT nanocomposites. The impact strength of the PS/HNTs nanocomposites was 300% higher than that of the neat PS. This paper presents a simple yet feasible method for the preparation of high-impact PS/halloysite nanocomposites.

Since polymer spherulites were observed using optical microscopy and single polymer crystals were prepared from solution,1,2 the internal structure of polymer spherulites has been investigated widely with electron microscopy.3-9 For most crystalline polymers, it is generally accepted that spherulites are developed from a single crystal through unidirectional growth, and the spherical shape is attained through continuous splaying apart and occasional branching of lamellae,5 though there are ongoing debates concerning the details of the branching in the literature. More recently, atomic force microscopy (AFM) has been utilized to study the organization of spherulites and the crystallization process of polymers.10,11 A copolymer, poly(bisphenol A-co-octane),12 was synthesized with the following structure

Novel polymer crystalline structures containing micrometer-sized concentric rings (or bands) were observed in thin poly(bisphenol A hexane ether) (BA-C6) films. The origin of the banded structures was found to be different from that of traditional banded spherulites in polymer systems. Analyses based on optical microscopy (OM) and atomic force microscopy (AFM) revealed that the banded structures contained alternating ridge and valley bands of polymer crystals in the flat-on orientation. No lamellar twisting was observed within the concentric-ringed structures, which were developed as a result of the formation of a depletion zone during crystallization. The formation of a depletion zone was determined to be caused by the specific volume decrement between the crystal and the melt and by the diffusion of polymer chains to the fold surfaces of the flat-on lamellae. The height of the ridges and the interband widths could be adjusted by controlling the diffusion rate. Time-of-flight secondary ion mass spectrometry ion images showed higher concentrations of low-molecular-weight polymer chains on the surfaces of the ridges than in the valleys.

Branching of edge-on lamellae of poly(bisphenol A octane ether) (BA-C8) was studied at room temperature (21 +/- 1 degrees C) using real-time tapping mode atomic force microscopy (AFM). Lamellar branches were shown to develop from induced nuclei that had originated from lamellar defects, namely protruding cilia and loose loops, of parent lamellae. Induced nuclei appeared and also disappeared-a phenomenon observed first time by AFM. Induced nuclei are one of the possible origins for the branching of lamellae. Branching of edge-on lamellae can be induced by an AFM tip though the adjustment of the set-point amplitude ratio (r(sp)). Using an r(sp) smaller than 0.65, defects could be created on the lamellar surface, which gave rise to lamellar branches.