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This paper describes the first in-depth attempt to characterize thermally induced aging of polypropylene (PP) samples by near infrared (NIR) spectroscopy. Significant levels of variation in NIR bands associated with short (amorphous-dominated) and long (crystalline-dominated) helices was readily captured when PP samples were subjected to thermal aging treatment. Partial least squares (PLS) regression models derived from the NIR spectra indicated significant level of correlation between the actual and predicted elongations of the samples. Analysis of PLS scores and two-dimensional (2D) correlation spectra derived from the aged PP samples revealed inner working mechanism of the regression model. Namely, the aging treatment essentially induces compositional change in crystalline and amorphous structures of the PP samples, which eventually affect the variation of the PLS scores. Thus, by utilizing the scores, it becomes possible to predict the change in the elongation property of the aged PP sample.

A technique for analyzing infrared imaging data based on two-trace two-dimensional (2T2D) correlation analysis is presented to extract pertinent information underlying spectroscopic imaging data. In 2T2D correlation mapping, each spectrum in hyperspectral data is individually compared with a reference spectrum to generate 2T2D asynchronous correlation intensity at the x- and y-coordinates on a 2T2D correlation map. Asynchronous correlation intensity develops only when the signal contribution from a certain species becomes even more significant in the sample spectrum compared with the reference spectrum. This feature can be advantageously utilized to examine molecular interaction or an intermediate form of the component present in a system of interest. 2T2D correlation mapping is examined using Fourier transform infrared imaging data of polymer composites based on polypropylene grafted with maleic anhydride melt-mixed with silica spheres. Infrared images derived by using conventional visualization based on a single wavenumber (i.e., 1713 cm−1) are dominated with the overwhelming infrared absorbance induced by the normal maleic anhydride species, making the identification of subtle but pertinent changes in the composite system difficult. A 2T2D correlation map derived from the maleic anhydride/silica spheres composite developed a significant asynchronous correlation intensity between the infrared bands at 1695 and 1713 cm−1 around a specific region on the map where the maleic anhydride and silica spheres coexist. On the other hand, such a correlation pattern becomes less acute when the silica spheres is modified with the octadecyldimethyl group to prevent the hydrogen bonding with the maleic anhydride. It thus revealed that the silanol groups on the surface of the silica spheres substantially interact with the maleic anhydride via the development of the hydrogen bonding.

We have developed a novel in situ Fourier transform infrared (FTIR) spectroscopic imaging technique that can probe the changes in the chemical structures around the matrix–filler interface of polym...

We have developed a novel rheo-optical Fourier-transform infrared (FTIR) imaging technique that can probe the molecular-scale deformation behavior of a polymer matrix in composite materials. This rheo-optical FTIR imaging is based on in situ-polarized FTIR imaging of a polymer sample while it is being deformed by mechanical force. This imaging technique readily captures the orientation of the polymer molecules resulting from the applied strain. Analysis of the resulting FTIR imaging data by disrelation mapping makes it possible to further elucidate subtle but pertinent spectral variations arising from changes in the state of molecules within the spectroscopic images. In this study, the rheo-optical FTIR imaging is applied to analysis of the deformation behaviors of a composite composed of polypropylene containing hydroxyl groups (PPOH) and silica spheres (SS) to investigate matrix-filler adhesion of the composite. Our rheo-optical FTIR imaging analysis revealed selective inhibition of PPOH orientation at the matrix-filler interface during tensile deformation due to high matrix-filler adhesion via hydrogen bonding. The strong link between the PPOH matrix and SS filler efficiently restricts mobility of the matrix, resulting in the reinforcement of PPOH by addition of SS. Rheo-optical FTIR imaging is an effective tool for probing localized deformation behavior at the matrix-filler interface as well as achieving a better understanding of the correlation between matrix-filler adhesion and the effective reinforcement of composites.

Simultaneous improvement in the mechanical properties and lifetime of polymer nanocomposites is crucially significant to further extend the versatility of polymer materials and reduce environmental impact. In this study, we fabricated reinforced polypropylene (PP)-based nanocomposites with improved aging stability by the addition of surface-modified well-ordered silica nanospheres with a silane coupling agent (SCA) containing hindered phenol antioxidant as a filler. Uniform grafting of the SCA on the filler surface contributed to homogeneous dispersion of the filler into the matrix, leading to improved properties (e.g., stiffness and ductility) and uniform distribution of the antioxidant component into the entire nanocomposite by filler dispersion. The grafting of SCA also likely provides an inhibitory effect on antioxidant migration, which leads to loss of polymer stability during the aging process. This novel idea for the material design of PP-based nanocomposites, which simultaneously enhances their mechanical properties and lifetime, is promising for application in the fabrication of various types of polymer nanocomposites.

This study addresses the multiscale analysis of acrylic urethane networks (AUN). To establish the kinetic model for predicting AUN oxidation, this study considered the pure thermal oxidation of AUN at 160, 180, and 200 °C. Chemical changes were monitored using infrared spectroscopy. These indicated the presence of an imide, presumably generated from the oxidation of CH2 at the α-position of nitrogen. On the macromolecular and macroscopic scales, oxidation was shown to induce predominant crosslinking, leading to a drop in toughness (i.e., embrittlement). The novel kinetic model of AUN thermal aging was developed from a mechanistic scheme previously established for polyamide 11, by adding some extra paths of thermolytic alkyl radical formation, oxidative Nsingle bondH bonds decomposition and coupling of aminyl radicals.

The structural alteration of acrylic-urethane coatings, induced by photo-aging, and its temperature dependence, was investigated using positron annihilation lifetime spectroscopy and solvent swelling experiments. The results revealed a slight structural alteration due to photo-aging at 20 °C. On the other hand, a significant structural alteration occurred due to photo-aging at 60 °C, which resulted in a decrease in the pore size and total pore volume. To study the mechanism of such morphological changes, infrared spectra were measured before and after aging the samples. The results revealed the breakage of the urethane crosslink points and the generation of various photo-products including peroxide species that can form hydrogen bonds. This indicates the foundation of new physical and chemical crosslinks (different from the initial urethane linkage). Based on the chemical modifications, probable mechanisms of the internal morphological changes are proposed. Moreover, the changes are mainly due to an enhancement in the chain-mobility, due to the destruction of the polymer network and an increase in the inter-chain interactions. The results of this study reveal that significant internal structural alterations can occur after sufficient damage to the initial network structure. The proposed explanation is reasonable in relation to the temperature dependence of photo-induced structural alterations, and with respect to the molecular mobility and reaction ratio of photo-oxidation.

Degradation testing of nylon 6-based carbon fiber-reinforced thermoplastic (CFRTP) was performed by exposure to hot steam in a closed vessel. The degraded structure was investigated to understand the degradation mechanism. Aging-induced micro-cracking in the nylon 6 matrix of CFRTP indicated that internal stress was generated by changes in its local density, along with a decrease in the molecular weight due to hydrolysis. Aging process of nylon 6 increased the free volume hole size in the amorphous part and also induced crystallization, suggesting that the density of the amorphous part decreases with increasing crystallinity in the matrix. Therefore, the degradation mechanism of the CFRTP was proposed to begin with a change in the local density of nylon 6 owing to crystallization, followed by water infiltration and hydrolysis of the matrix. Stress due to density changes combined with reduced molecular weight forms micro-cracks, decreasing the mechanical strength of CFRTP.

Nanocomposites containing mesoporous silica (MPS) materials with various pore structures (SBA-15 and MCM-41 types) melt mixed into polypropylene (PP) or PP functionalized with hydroxyl groups (PPOH) were characterized by analytical pyrolysis techniques, such as evolved gas analysis (EGA)-mass spectrometry (MS) and heart-cut EGA-gas chromatography (GC)/MS, to evaluate the interactions between the polymer matrix and MPS and the pore filling of the MPS in the nanocomposite. The EGA-MS measurements revealed that nanocomposites with MPSs evolve specific degradation products, which can be attributed to strong interactions between the polymer molecules and the internal pores. The amount of these specific products increased upon increasing the pore size of the MPS and the hydroxyl content in the polymer matrix. Sufficiently large pores of MPS and high hydroxyl contents in the matrix appear to provide strong interactions because the MPS pores are well-filled with polymer molecules, which contributes to the improved physical properties of the nanocomposites. Nanocomposites containing mesoporous silica (MPS) materials with various pore structures (SBA-15 and MCM-41 types) melt mixed into polypropylene (PP) or PP functionalized with hydroxyl groups (PPOH) were characterized by analytical pyrolysis techniques, such as evolved gas analysis (EGA)-mass spectrometry (MS) and heart-cut EGA-gas chromatography (GC)/MS, to evaluate the interactions between the polymer matrix and MPS and the pore filling of the MPS in the nanocomposite. The EGA-MS measurements revealed that nanocomposites with MPSs evolve specific degradation products, which can be attributed to strong interactions between the polymer molecules and the internal pores. The amount of these specific products increased upon increasing the pore size of the MPS and the hydroxyl content in the polymer matrix. Sufficiently large pores of MPS and high hydroxyl contents in the matrix appear to provide strong interactions because the MPS pores are well-filled with polymer molecules, which contributes to the improved physical properties of the nanocomposites.

The long-range objective of this study is to provide better understanding of the relationship between the structures and properties of PP-based nanocomposites containing mesoporous silica (MPS). In this investigation, nanocomposites composed of MPSs with various porosity structures (two types of Santa Barbara Amorphous No. 15 (SBA-15) with pores of 4.4 or 8.0 nm, and Mobile Composition of Matter No. 41 (MCM-41) with pores of 2.9 nm) and polypropylene (PP) or functionalized PP containing hydroxyl groups (PPOH) were developed. Their physical properties were then evaluated. The nanocomposite containing PPOH and SBA-15 with a large pore size (SBA-15-L) showed higher toughness, stiffness, and transparency than the other nanocomposites. Our results indicated that the larger pore size of SBA-15-L and the high affinity between PPOH and the MPS surface led to an efficient pore-filled state of SBA-15-L with polymer molecules, forming a nanocomposite with better mechanical strength and transparency. Nanocomposites composed of mesoporous silica (MPS) materials with various porosity structures (two types of SBA-15 with pores of 4.4 or 8.0 nm, and MCM-41 with pores of 2.9 nm and polypropylene (PP) or functionalized PP containing hydroxyl groups (PPOH) were developed. The nanocomposite containing PPOH and SBA-15 with a pore of 8.0 nm showed higher toughness, stiffness, and transparency than the other nanocomposites.

We have developed a three-way evolved gas analysis-mass spectrometry technique combined with principal component analysis (EGA-MS-PCA) to probe the interfacial state between matrix and filler in poly(styrene-b-butadiene-b-styrene) (SBS) nanocomposites containing graphene nanoplatelets (GNPs). Although the peaks arising from the polystyrene and polybutadiene components present in the system were readily captured, the different patterns of peak intensities, which vary according to the applied temperature and GNP content, make interpretation of the data difficult. The data sets are thus subjected to mathematical decomposition based on principal component analysis (PCA) to selectively derive essential information. The EGA-MS-PCA process reveals that the inclusion of GNPs essentially works to restrict the decomposition of the polystyrene component in the SBS sample, mostly indicating the formation of a π–π stacking interaction between the SBS and GNPs. This observation, in turn, provides in-depth understanding that is likely to lead to stiffness of SBS by incorporation of GNPs.

We developed novel polypropylene (PP)/silica nanocomposites using PP and silica nanospheres (SNSs) combined with poly(5-hexen-1-ol-co-propylene) (PPOH), which is a functionalized PP containing hydroxyl groups that was assumed to play a role as not only an elastomer but also an interface modifier. Since the affinity between the PP matrix and silica filler was expected to be improved by blending with PPOH, its influence on the mechanical properties, structure, and toughness of the ternary composites was examined in detail to provide a better understanding of the role of the matrix-filler affinity on the mechanical properties. The dispersity of the SNSs in the fabricated PP/PPOH/SNS nanocomposite was improved by increasing the hydroxyl group content of PPOH due to the enhanced affinity between PPOH and the SNSs. The SNSs in the composite with PPOH containing 6.4 mol% hydroxyl groups (PPOH6.4) were almost dispersed in the microscale domain, while the SNSs in the composite with 1.3 mol% hydroxy groups (PPOH1.3) were considerably aggregated. The toughness of the nanocomposite was noticeably improved by blending PPOH6.4 without a significant loss of stiffness. In contrast, the toughness was hardly improved using PPOH1.3. Therefore, both the fine dispersion of the SNSs and the excellent affinity between PPOH6.4 and the SNSs contributed to the good balance of toughness and stiffness of the PP/PPOH/SNS nanocomposite.

Functionalized polypropylene with hydroxyl group (PPOH) nanocomposites with varying chemical structures in filler-matrix interfaces were examined by rheo-optical near-infrared measurements combined with two-dimensional correlation spectroscopy, to provide a better understanding of the reinforcement mechanism of nanocomposites. PPOH nanocomposites were fabricated by melt-mixing (i) silica nanospheres (SNS) and (ii) SNS modified with surfactant (mSNS). The decrease in the asynchronous correlation intensity from PPOH to SNS/PPOH indicated that the tensile deformation of amorphous and crystalline occurred simultaneously. These observations implied that the high interfacial adhesion between filler and matrix restricted the deformation of amorphous. This mechanism seems to contribute to the improvement in mechanical strength of the composite. The asynchronous correlation intensity of mSNS/PPOH was higher than that of SNS/PPOH, indicating that a certain level of deformation of the amorphous was allowed. It is therefore likely that the surface modification of SNS prevented filler-matrix interactions, leading to relatively low tensile strength of mSNS/PPOH. Thus, the techniques based on NIR spectroscopy clarify the effects of the filler-matrix interfacial adhesion of nanocomposites on the behavior of the crystalline and amorphous components during tensile testing, and may be generally applicable to evaluate filler-matrix adhesion behavior of a wide range of polymer nanocomposite systems.

Application of the two-dimensional (2D) correlation spectroscopy is extended to Chemiluminescence (CL) spectra of isotactic polypropylene (iPP) under thermally induced oxidation. Upon heating, the polymer chains of the iPP undergoes scissoring and fragmentation to develop several intermediates. While different chemical species provides the emission at different wavelength regions, entire feature of the time-dependent CL spectra of the iPP samples were complicated by the presence of overlapped contributions from singlet oxygen (1O2) and carbonyl species within sample. 2D correlation spectra showed notable enhancement of the spectral resolution to provide penetrating insight into the thermodynamics of the polymer system. For example, the, oxidation induce scissoring and fragmentation of the polymer chains to develop the carbonyl group. Further reaction results in the consumption of the carbonyl species and subsequent production of different 1O2 species each developed in different manner. Consequently, key information on the thermal oxidation can be extracted in a surprisingly simple manner without any analytical expression for the actual response curves of spectral intensity signals during the reaction.

We fabricated nanocomposites by dispersing uniform-sized silica nanospheres (SNSs, 49–282 nm, 0–30 wt%) into polypropylene (PP) and two types of functionalized PP to clarify the effects of matrix-filler interfacial adhesion forces on the mechanical properties in PP-based nanocomposites. Since there is good affinity between silica surfaces and hydroxyl group in PP, poly(5-hexen-1-ol-co-propylene) with 1.3 and 6.4 mol% of hydroxyl groups were employed as functionalized PP (PPOH). Tensile tests revealed that some mechanical properties of the composites with PPOH were higher than those with PP. In particular, composites with PPOH maintained high ductility, whereas the ductility of composites with PP were significantly reduced by dispersing SNSs. Fourier-transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) studies indicated the formation of hydrogen bonds between PPOH and the silica surface, which are attributed to the high ductility.

We propose a technique for evaluating the compatibilization effect of maleic anhydride-grafted polypropylene (MAPP) introduced into glass fiber reinforced polypropylene by probing chemical structures using Fourier transform infrared (FTIR) microscopy. The dispersion state of MAPP in the composites was investigated by FTIR imaging constructed with integrated spectral intensity arising from carbonyl groups. MAPP was predominantly distributed around the glass fibers, due to the formation of interactions between the carbonyl groups in MAPP and the surface silanol groups on the fibers. The effects of interfacial interactions on matrix-fiber adhesion of the fiber composite were confirmed by observation of a fracture surface, using FTIR imaging, after tensile testing. The presence of polymer adhered to the fiber was detected. This revealed cohesive failure to occur in the matrix portion, attributable to improved interfacial adhesion. The addition of MAPP is therefore essential to improve matrix-filler adhesion, which contributes to enhanced strength and ductility by efficient stress transfer and prevention of fracturing at the matrix-fiber interface. This characterization technique can be utilized as a generally applicable tool to reveal the mechanisms of compatibilization of polymer composites.

The molecular architecture changes of crosslinked urethane during photo-oxidation was investigated by Fourier transform infrared spectroscopy (FTIR) in combination with two-dimensional (2D) correlation analysis. The 2D correlation FTIR spectroscopy provided insight into molecular architectural dynamics during photo-aging, where the sequential order of peak changes was determined upon perturbation with photo-aging. Photo-oxidation was monitored from the decrease in the peak intensity at 1537 cm−1 (attributed to the urethane group) and the generation of the hydrogen bonded C =O groups at 1698 cm−1 immediately after urethane decomposition. Several notable peaks appeared (1712, 1650, and 1750 cm−1) in the later stages, which were attributed to the free photo-oxidative product. In summary, photo-oxidation involved a cleavage of urethane crosslink and generation of end groups that formed hydrogen bonds with surrounding hydrogen bonding sites. Further degradation of the free photo-products was observed likely because of the small number of accessible hydrogen bonding sites due to the increasing heterogeneity of the internal structure.

Submolecular-level variation of polypropylene (PP) caused by aging treatment is studied by two-dimensional (2D) small-angle X-ray scattering (SAXS) in conjunction with 2D correlation spectroscopy. PP samples were prepared by a T-die extrusion method and then probed by 2D SAXS. Direction-depending SAXS profile data were obtained by extrusion the SAXS intensities along the direction from 90° (i.e. direction of extrusion) to 120° on the 2D SAXS image. 2D correlation spectra derived from the SAXS profiles of the PP samples revealed the detailed orientations of the lamellae in the polymer system. For example, the development of asynchronous correlation peaks indicates that significant portion of the lamellae in the initial PP sample aligns to the direction of the extrusion. These lamellae tend to go through subsequent crystallization to increase the thickness during the cooling process, while the polymer chain inclined to the direction of the extrusion does not undergo such sufficient level of crystallization. It was also revealed that the aging treatment based on the heating well above glass transition temperature of the PP (ca. 0 °C) essentially provides additional crystalline growth especially to the inclined lamellae.

Structural changes induced by photo-aging have significant influence on material properties. The prediction of the period prior to the onset of significant morphological changes is useful in determining material service lifetime. We assume “degelation” to be the starting point of significant morphological change during photo-aging. Herein, we demonstrated the relationship between such time and the “degelation” phenomenon for an acrylic-urethane network polymer. We also derived a “degelation” theory considering network imperfections, e.g. dangling chains and looping chains. This provides a more accurate representation of reactive curing polymers widely used in industries. Lastly, we estimated the “imperfection degree” by comparing the number of elastically active chains obtained from a swelling experiment with the theoretically derived number. In this system, samples may originally possess approximately 10% network imperfection and it influences on the degelation period in aging process. Our study may potentially contribute to a more accurate prediction of the onset of significant structural change.

We demonstrate a Fourier transform infrared (FTIR) spectroscopic imaging combined with two-dimensional (2D) correlation analysis to elucidate matrix-filler interaction of polymer composites. Composite of maleic anhydride grafted polypropylene (MAPP) and silica sphere (SS) was fabricated. The FTIR image and disrelation map derived from sets of FTIR spectra suggest that the maleic anhydride groups in MAPP surround the SS surface and interact with the silanol on the surfaces of SS via hydrogen bonding. This clear link between MAPP and SS indicates that MAPP can be utilized as a suitable amphiphilic compatibilizer for an SS filler when it is mixed with hydrophobic polymer. FTIR imaging analysis was then further extended to categorize the interfacial states of more complicated polymer composites consisting of polypropylene (PP)/SS containing MAPP as a compatibilizer. Probing the interfacial chemical state using FTIR imaging revealed the interaction between MAPP and SS to contribute to improved elastic modulus of PP/MAPP/SS.

The degradation of poly(ethylene terephthalate) (PET) was investigated through a weathering test by using a xenon weather meter. The degraded structure was evaluated by means of gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and positron annihilation lifetime spectroscopy (PALS). The GPC results indicated a decrease of number average molecular weight and a broadening of polydispersity with the degradation of PET, probably due to chain scission and some networking reactions. The DSC results indicated that the crystallinity index was changed through the weathering test. However, the change of crystallinity was poorly correlated with the progress of degradation. In the Tan δ measurement by DMA, suppression of molecular mobility during the degradation was implied by the increase in T g with increasing exposure time. The PALS results revealed that the free-volume hole size decreased with increasing exposure time. The decrease in the free-volume hole size can be attributed to the interaction between functional groups produced by hydrolysis or photochemical chain scission. The change of properties and structure in the amorphous part of PET was found to be correlated with the progress of the degradation in the weathering test.

Two types of commercial cellulose triacetate hollow-fiber membranes with different water fluxes, apposite for a reverse osmosis separation process, were investigated by means of positron annihilation lifetime spectroscopy with a 22Na-radioisotope-based energy-tunable positron beam, in order to elucidate a depth profile of the free-volume hole size in a subnanoscopic viewpoint. The lifetimes of ortho-positronium (o-Ps), the triplet positron-electron pair, for the two membranes were measured as a function of positron incident energy E. The E dependence of the hole size, quantified from the o-Ps lifetime, indicated that the separation-active dense layers with the smallest hole sizes are located at the near-surface region for both the membranes. The ratio of the dense-layer thicknesses for the two membranes was estimated to be more than 50% of the ratio of the respective effective thicknesses calculated from the water flux based on Darcy's law. The result signified that the dense layer with the smallest hole size at the near-surface region considerably contributes to the difference in the water flux.

A rheo-optical characterization technique based on the combination of near-infrared (NIR) spectroscopy and mechanical analysis was applied to the nanocomposite consisting of hydroxyl-functionalized polypropylene (PPOH) and mesoporous silica (MPS) to probe the deformation behavior. Substantial levels of spectral changes of NIR spectral features were captured when the polymer samples underwent tensile deformation. Sets of spectra were subjected to projection treatment to remove the effect of baseline fluctuations and thickness change inevitably caused by the tensile deformation of the sample. Then, two-trace two-dimensional (2T2D) correlation spectroscopy was applied to the pretreated spectra to elucidate spectroscopic signature associated with the difference between the initial and deformed samples. An asynchronous correlation peak appears between the bands at 1720 and 1700 nm respectively reflecting the contributions of predominantly amorphous and crystalline component of the PPOH, indicating the predominant variation of amorphous structure followed by that of crystalline structure. In addition, the predominant spectral change related to the amorphous band becomes even more acute by including the MPS with large pores. It is hence likely that the larger pore size of the MPS confines the more amorphous structure, which, in turn, causes simultaneous reorientation of the polymer chains in the amorphous region during the elastic deformation. Consequently, the incorporation of the MPS selectively restricts the deformation of the amorphous structure which eventually provides the obvious increase in the mechanical property of the PPOH polymer.

Two fulleropyrrolidine derivatives with the benzophenone moiety were synthesized based on a molecular design that suppresses their crystallization. The organic photovoltaic devices using the fuller...

Polypropylene (PP) and its derivatives, poly(5-hexen-1-ol-co-propylene) (PPOH) and poly(1-hexene-co-propylene) (PPH), were comprehensively investigated by means of wide-angle X-ray diffraction, dynamic mechanical analysis (DMA), 1H pulsed nuclear magnetic resonance (NMR), infrared (IR), and positron annihilation lifetime (PAL) techniques. The deduced nanoscopic amorphous structure was discussed in comparison with the mechanical properties such as tensile strength. Introducing polar hexenol and nonpolar hexene comonomers into PP chains resulted in a significant reduction of the crystallinity for both the derivatives, which failed to explain the anomalous higher tensile strength of PPOH. The long decay T2 observation from NMR indicated a lower chain mobility in the amorphous region of PPOH compared to PPH, consistent with the DMA analysis, providing a higher glass transition temperature for the former polymer. The PAL and IR results signified reduced free-volume size along with hydrogen bond formation in th...

We studied chemiluminescence spectroscopy to develop an evaluation method for organic material degradation. The thermal oxidation of oleic acid as a monounsaturated fatty acid was investigated using chemiluminescence measurements. The obtained spectra indicated that the luminescence consisted of several peaks, including peaks for singlet oxygen and excited carbonyls. A detailed analysis of the nuclear magnetic resonance and infrared absorption spectra allowed us to determine the probable structures of the oxidative products. The relationship between the spectrum and the analyzed structure implied that the wavelength of the carbonyl group emission peak shifted as a result of the structure.

A quick method involving the control of heat and water vapor pressure for preparing moisture-saturated carbon fiber-reinforced plastics (CFRP, 8 unidirectional prepreg layers, 1.5 mm thickness, epoxy resin) has been developed. The moisture-saturated CFRP sample was obtained at 120 °C and 0.2 MPa water vapor in 72 h by this method using a sterilizer (autoclave). The bending strength and viscoelastic properties measured by a dynamic mechanical analysis (DMA) remained unchanged during repetitive saturation and drying steps. No degradation and molecular structural change occurred. Furthermore an accelerated ageing test with two ageing factors, i.e., heat and moisture was developed and performed at 140–160 °C and 0.36–0.62 MPa water vapor pressure by using a sealed pressure-proof stainless steel vessel (autoclave). The bending strength of the sample decreased from 1107 to 319 MPa at 160 °C and 0.63 MPa water vapor pressure in 9 days. Degraded samples were analyzed by DMA. The degree of degradation for samples was analyzed by DMA. CFRP and degraded CFRP samples were analyzed by using a surface and interfacial cutting analysis system (SAICAS) and an electron probe micro-analyzer (EPMA) equipped in a scanning electron microscope.

PET films were degraded at temperature higher than 100°C with steam and xenon light by using the newly developed system. Degradation products obtained using the proposed and conventional systems were essentially the same, as indicated by the similar increase in the intensity of the carbonyl peak near 1685 cm−1 in the FT-IR spectra of irradiated specimens and spectrum of original PET film. Elastic moduli derived from the stress-strain (SS) curves obtained in tensile tests were almost the same in the case of the proposed and conventional systems and were independent of the heating temperature, light intensity, and irradiation time. Tensile strength of degraded PET films decreases with increasing heating temperature. Tensile strengths of PET films degraded at same temperature decrease linearly with increasing intensity of xenon light. The lifetime at 90% strength of PET films was calculated. Attempts were made to express this lifetime as functions of the light intensity and the reciprocal of the absolute temperature by using the Eyring model. Estimated lifetime 15.9 h of tensile test using Eyring model for PET film agreed with the lifetime 22.7 h derived from data measured using the xenon weather meter.

Polypropylene (PP) derivatives, prepared with different α-olefin comonomers of hexane and hexenol, were investigated using the positron annihilation lifetime technique. The free-volume hole sizes for the present polymers were quantified from the long-lived ortho-positronium (o-Ps) lifetimes. In contrast to the case of nonpolar, introduction of the polar hexenol into PP reduced the o-Ps lifetimes and the hole sizes derived from them. This indicates that the interchain interaction due to the hydrogen bonds in the amorphous region is much stronger than the enhancement of the segmental motion due to the butyl long branch. A comparison of the o-Ps lifetimes with the corresponding tensile strength suggested significant contribution of the subnanostructure in the amorphous region to the mechanical property.

We describe the synthesis of a styrene–ethylene copolymer using a trivalent titanium-based polymerization catalyst system, tris(acetylacetonate)titanium (Ti(acac)3), combined with triisobutylaluminum-modified methylaluminoxane. Gel-permeation chromatography measurement revealed that copolymerization using the above-mentioned catalyst system yielded a mixture of two different polymers. 13C nuclear magnetic resonance (NMR) analysis of the Soxhlet-extracted fractions indicated that the insoluble part contained a long ethylene–ethylene sequence and an isolated styrene unit, whereas the soluble part contained a syndiotactic styrene–styrene sequence with ethylene units adjacent to continuous styrene units. The ratio of the styrene–styrene sequence to the styrene–ethylene joint part of the Soxhlet-soluble fraction, estimated from the NMR resonances, increased with the styrene content. The melting temperature of the Soxhlet-soluble fraction also increased with the (styrene–styrene)/(styrene–ethylene) ratio of the polymers. These two results together indicate that a block-like copolymer was produced that contained long syndiotactic polystyrene portions separated by ethylene units. We describe the synthesis of a styrene–ethylene copolymer using a trivalent titanium-based polymerization catalyst system, tris(acetylacetonate)titanium/triisobutylaluminum-modified methylaluminoxane (MMAO). The catalyst system yielded a mixture of two different polymers. 13C nuclear magnetic resonance analysis of Soxhlet-extracted fractions indicated that the Soxhlet-soluble part contains the syndiotactic styrene–styrene sequence and the ethylene units adjacent to continuous styrene units. Consideration about a relation among sequence distribution, styrene content and thermal property data reasonably indicates that the block-like copolymer was produced, which contains the long syndiotactic polystyrene portions separated by the ethylene units.

This article reports the synthesis and characterization of an extremely high thermostable cyclic olefin copolymer with advanced optical properties resulting from the vinyl addition copolymerization of norbornene with styrene catalyzed by a substituted fluorenylamidodimethyltitanium catalyst [Me 2 Si(3,6-tBu 2 Flu)(tBuN)]TiMe 2 activated with a [Ph 3 C] [B(C 6 F 5 ) 4 ]/Al(iBu) 3 cocatalyst using o-dichlorobenzene as solvent. The prepared copolymer possesses a glass transition temperature as high as polyimide (Tg > 300 °C) and a high transmittance which is comparable with that of the conventional optical resins ([T] > 90%). The incorporation of polystyrene, which exhibits a negative birefringence into the vinyl-added polynorbornene that possesses an intrinsic positive birefringence, effectively reduced the birefringent magnitude of the norbornene-styrene copolymer due to a mutual compensation between these opposite-sign birefringences. The absence of any functional and aromatic heterocyclic groups and the presence of highly hydrophobic saturated bicyclic rings in the copolymer main chains effectively prevented the diffusion of water/oxygen and thus enhanced the dimensional and optical stabilities of the material. Preliminary results on the characterization of the thermal stability, mechanical, and optical properties of the vinyl-added norbornene-styrene copolymers indicate that they satisfy all the rigorous requirements for a polymer to be applied as a flexible substrate for the manufacturing of the flexible displays.

The generation of acetic acid from the ethylene vinyl acetate (EVA) encapsulant in crystalline Si photovoltaic (PV) modules was investigated by free-volume analysis with positron annihilation lifetime spectroscopy (PALS). The reduction in size of a free-volume hole attributable to deacetylation was clearly observed near the surface of the EVA encapsulant for a module aged in a damp heat (DH) test following UV irradiation (hereafter referred to as the post-UV DH test). Deacetylation in the post-UV DH test was considerable compared with that in a normal DH test. The depth profile of the size of a free-volume hole in a sample exposed outdoors was revealed to be very similar to that obtained in the post-UV DH test. This strongly implies that deacetylation was promoted near the interface between EVA and other components in the accelerated degradation test as well as by outdoor exposure.

Additive effects of diisobutylaluminum hydride (DiBAL-H) was studied in copolymerization of propylene and 1,3-butadiene with a series of C 2 -symmetric ansa-bis(indenyl)zirconocene derivatives, i.e., rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride ( 4Ph ), dichloride, rac-dimethylsilylbis(2-methyl-benzoindenyl)zirconium dichloride ( Bz ), rac-dimethylsilylbis(2-methyl-indenyl) zirconium dichloride ( 2Me ), rac-dimethylsilylbis(1-indenyl)zirconium dichloride ( 1-Ind ), rac -ethylenebis(1-indenyl)zirconium dichloride ( Et-Ind ), activated by modified methylaluminoxane (MMAO). Without DiBAL-H, the activity of the copolymerization decreased in the following order, 2Me > 1-Ind > Et-Ind > 4Ph ≈ Bz , whereas butadiene content decreased in the following order, 4Ph > Bz ≥ Et-Ind ≥ 1-Ind > 2Me ≈ 0.1 mol%. The addition of DiBAL-H affected the activity but hardly changed the butadiene content. The copolymer obtained without DiBAL-H contained the butadiene units of 1,2-insertion (1,2-BD) and 1,4-insertion (1,4-BD). The addition of DiBAL-H decreased the amount of 1,4-BD and produced hydrogenated 1,4-BD in the 4Ph and Bz systems accompanied by the increase of the copolymerization activity. The additive effect of other alkylaluminums was investigated in the Bz system, and DEAL-H was found to show the similar effects with DiBAL-H. The 13 C NMR analysis of the polymer terminated with deutrated methanol indicated the hydroalumination of 1,4-BD in the Bz system. Hydroxyl groups can be also introduced by oxidative cleavages of the Al–C bonds.

Styrene polymerization was carried out by a simple half-titanocene complex [cyclopentadienyltitanium trichloride] (CpTiCl 3 ) and pentamethyl [cyclopentadienyltitanium trichloride] (Cp*TiCl 3 ) combined with methylaluminoxane (MAO) as a cocatalyst. The effects of addition of 2,6-diisopropylphenol on the catalytic activity of the above catalytic systems and the microstructure of the resulting polymer were investigated. The results of the above experiments showed that the addition of the 2,6-diisopropylphenol changed the catalytic performance of the above catalytic systems, in terms of catalytic activity of the metal complexes and microstructure, molecular weight and molecular weight distribution of polystyrene synthesized. The yields of polystyrene of the above polymerization reactions indicated that the 2,6-diisopropylphenol enhanced the catalytic activity of both the CpTiCl 3 /MAO and Cp*TiCl 3 /MAO catalyst systems. Further Soxhlet extraction of the polymer was conducted by boiling acetone for 6 h to get pure syndiotactic polystyrene. The microstructure of polystyrene obtained by the above polymerization reactions was investigated by 13 C NMR, GPC and DSC. Results indicated the formation of syndiotactic polystyrene in the absence of phenol and in low concentration of phenol. On the other hand, in the presence of excess phenol, the polystyrene produced was found to be completely atactic in nature. The appearance of monomodal peaks and narrow polydispersity in the GPC results of polystyrenes obtained in all the above polymerizations indicated that the polymerization was only coordination in nature.

This article reports an original method to control the birefringent property of the cyclic olefin copolymer, which has been recently commercialized as a new type of optical resins, via introduction of a third monomer that possesses a negative birefringence into the cyclic olefin copolymer that exhibits an inherently positive birefringence. The mutual compensation between these opposite-sign birefringences effectively reduced the birefringent magnitude of the corresponding terpolymer. In fact, terpolymerization of norbornene (N), ethylene (E), and styrene (S), in which S exhibits a negative birefringence regarding to the positive birefringence of the NE copolymer was successfully prepared using fluorenylamidodimethyltitanium-based catalyst, yielding NES terpolymers with controllable birefringent property. Especially, when the S content in the NES terpolymer was controlled at optimum values, it is possible to synthesize a new type of the cyclic olefin copolymer that exhibits an extremely low birefringent magnitude close to zero regardless of high degrees of chain orientation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7395–7400, 2008

We inclusively investigated polymerization behavior and structure of copolymer in the copolymerization of propylene and alkylaluminum-protected polar allyl monomers. The control of the arrangement of polar group in the copolymer was discussed. It was proved that the location of polar group could be controlled by zirconocene catalyst and a kind of polar monomer. The indenyl or the 2-methylindenyl ligands of zirconocene were favored to produce end-functionalized polymers. It was also found that the trimethylaluminum-protected allylamine and triisobutylaluminum-protected allylmercaptan had superior ability in the synthesis of end-functionalized polypropylene. On the other hand, the 2-methyl-4-phenylindenyl ligand produced the copolymers containing both the end-polar unit and inner-polar unit at the polymer chains. Terpolymerization of propylene, polar allyl monomer, and 5-hexen-1-ol was also conducted. The NMR study of the terpolymer revealed that both the 5-hexen-1-ol and the polar allyl monomer were incorporated into the polymer chain. It has also become apparent that the polar allyl monomer units predominantly occupied the chain end, while the 5-hexen-1-ol units were located at the inner of main chain. Consequently, we have achieved the synthesis of functionalized polypropylene in which the arrangement of polar group was precisely controlled. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1738–1748, 2008

Poly(propylene-ran-1,3-butadiene) was synthesized using isospecific zirconocene catalysts and converted to telechelic isotactic polypropylene by metathesis degradation with ethylene. The copolymers obtained with isospecific C2-symmetric zirconocene catalysts activated with modified methylaluminoxane (MMAO) had 1,4-inserted butadiene units (1,4-BD) and 1,2-inserted units (1,2-BD) in the isotactic polypropylene chain. The selectivity of butadiene towards 1,4-BD incorporation was high up to 95% using rac-dimethylsilylbis(1-indenyl)zirconium dichloride (Cat-A)/MMAO. The molar ratio of propylene to butadiene in the feed regulated the number-average molecular weight (Mn) and the butadiene contents of the polymer produced. Metathesis degradations of the copolymer with ethylene were conducted with a WCI6/SnMe4/propyl acetate catalyst system. The 1H NMR spectra before and after the degradation indicated that the polymers degraded by ethylene had vinyl groups at both chain ends in high selectivity. The analysis of the chain scission products clarified the chain end structures of the poly(propylene-ran-1,3-butadiene). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5731–5740, 2007