Calculation of polymer blend compositions from Raman spectra: A new method based on parameter estimation techniques

A simple method to determine polymer blend compositions from their Raman spectra is presented. The method is based on expanding linearly the experimentally measured Raman spectrum of the blend, in terms of Raman spectra of pure components. A smooth function has also been included in the linear expansion to take into account the fluorescence interference, inherent to Raman spectroscopy. The coefficients of the linear expansion that give the best fit to the experimentally measured Raman spectrum of the blend are found by using a standard method of parameter estimation (Marquardt–Levenberg). These coefficients are directly related to the blend composition via a simple calibration procedure. Unlike standard methods of processing Raman spectra as deconvolution and curve‐fitting—which use Gaussian and/or Lorentzian functions to approximate the spectrum bands—the proposed method does not require either baseline correction or previous knowledge of peak parameters. Also, this method requires less CPU time than deconvolution and curve‐fitting procedures, and it is easy to automate. The proposed method has been applied to blends made out of two polymers: Polystyrene (PS) and poly(phenylene oxide) (PPO), to test its precision and consistency. Excellent agreement was found between calculated and expected blend compositions. Also, the reconstructed spectra agree very well with the experimentally measured blend spectra. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1013–1023, 2000     

Theoretical and experimental studies on the Raman spectra of electrosynthesized polynaphthalene

Polynaphthalene (Pnap) was electrosynthesized through the direct oxidation of naphthalene in boron trifluoride diethyl etherate and was characterized with IR and Raman spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy, and thermogravimetric analysis. Raman spectra of oligonaphthalene were calculated with Gaussian 98 at the B3LYP/6‐31G* level. Combining the computational and experimental results, we assigned the Raman bands of pristine Pnap. The Raman bands related to the chain‐stretching vibrations of Pnap around 1600 cm^?1 shifted to higher wave numbers as the polymerization degree increased. This phenomenon was in contrast to that of other conducting polymers bearing simple aromatic rings, such as polythiophene and polyfuran. The reason was that the condensed ring of Pnap and the steric repulsion of the interring hydrogen atoms prevented the elongation of conjugation sequences with the polymer chain length. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 241–251, 2005     

Modification of surface properties of polyethylene by perfluoropolyether blending

The preparation of a stabile blend from thermoplastic polymer and lubricating additive was studied with high density polyethylene (HDPE) and perfluoropolyether (PFPE). PFPE was melt blended within HDPE by injection molding. The chemical composition of the mixtures, the relative amount of PFPE on the surface, and the nature of the surface were studied by three surface sensitive methods: attenuated total reflectance infrared (ATR‐IR) spectroscopy, secondary ion mass spectroscopy (SIMS), and contact angle (CA) measurement. All the blends exhibited improved hydrophobicity. CA and SIMS gave a maximum response when about 2.0 wt % PFPE was added, whereas ATR‐IR spectroscopy gave maximum response for an addition of about 3.0 wt %. No changes in surface properties were observed when samples were reanalyzed about 1–4 months after preparation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2252–2258, 2005     

Near‐infrared spectroscopic studies on the cure behaviors of the CAE/DGEBA blend system initiated by a thermal latent catalyst

The latent properties and cure behaviors of an epoxy blend system based on cycloaliphatic epoxy (CAE) and diglycidyl ether of bisphenol A (DGEBA) epoxy containing N‐benzylpyrazinium hexafluoroantimonate (BPH) as a thermal latent initiator were investigated with near‐infrared (N‐IR) spectroscopy. The assignments of the latent properties and cure kinetics were performed by the measurements of the N‐IR reflectance for epoxide and hydroxyl functional groups at different temperatures and compositions. As a result, this system showed more than one type of reaction, and BPH was an excellent thermal latent catalyst without any coinitiator. The cure behaviors were identified by the changes in the absorption intensity of the hydroxyl groups at 7100 cm⁻¹ with different composition ratios. Moreover, characteristic N‐IR band assignments were used to evaluate the reactive kinetics and were shown to be an appropriate method for studying the cure behaviors of the CAE/DGEBA blend system containing a thermal latent catalyst. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 326–331, 2001     

Synthesis,characterization, thermal properties,and antimicrobial activity of 4‐chloro‐3‐methyl phenyl methacrylate/8‐quinolinyl methacrylate copolymers

4‐Chloro‐3‐methyl phenyl methacrylate (CMPM) and 8‐quinolinyl methacrylate (8‐QMA) were synthesized through the reaction of 4‐chloro‐3‐methyl phenol and 8‐hydroxy quinoline, respectively, with methacryloyl chloride. The homopolymers and copolymers were prepared by free‐radical polymerization with azobisisobutyronitrile as the initiator at 70 °C. Copolymers of CMPM and 8‐QMA of different compositions were prepared. The monomers were characterized with IR spectroscopy and ¹H NMR techniques. The copolymers were characterized with IR spectroscopy. UV spectroscopy was used to obtain the compositions of the copolymers. The monomer reactivity ratios were calculated with the Fineman–Ross method. The molecular weights and polydispersity values of the copolymers were determined with gel permeation chromatography. The thermal stability of the polymers was evaluated with thermogravimetric analysis under a nitrogen atmosphere. The homopolymers and copolymers were tested for their antimicrobial activity againstbacteria, fungi, and yeast. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 157–167, 2005     

Kinetic study of the solution polymerization of methacrylamide initiated with potassium persulfate using in situ Raman spectroscopy and band‐target entropy minimization

In this paper, the use of in situ Raman spectroscopy together with a novel multivariate data analysis method, band‐target entropy minimization (BTEM), is discussed to monitor the solution polymerization of methacrylamide in aqueous medium. Although FTIR spectroscopy is a more popular spectroscopic technique for polymer characterization and in situ polymerization monitoring, Raman spectroscopy is selected over FTIR in the current study. This is because water has very strong and broad infrared absorption bands and thus masks most of the other infrared signals contributed from monomer and polymer. On the contrary, water has very weak Raman scattering and thus it does not interfere the other Raman signals. The polymerization was initiated with potassium persulfate (KPS). A series of experiments were carried out varying initial monomer concentration, initial KPS concentration, and polymerization temperature. In situ Raman spectroscopy was used to monitor the polymerizing mixture and measure the compositions. The collected reaction spectra were subjected to BTEM to elucidate the pure component spectra, and then determine the conversion of monomer. The conversion data was then used to obtain kinetic parameters for the polymerization. The rate of consumption of monomers was found to follow the expression R = k_eff [I]^0.55[M]^1.41. The activation energy of the system was estimated at 121 kJ/mol. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5697–5704, 2007     

Extinction coefficient of polyolefin foams

The extinction coefficient of a collection of polyolefin foams was investigated experimentally and theoretically. Transmittance spectra were measured with Fourier transform infrared spectroscopy (FTIR) for samples of various thicknesses and different chemical compositions, densities, colors and structural characteristics. The extinction coefficients were then calculated by applying Beer's law. The results showed that the extinction coefficient decreased with the mean cell size and that this was the main structural parameter influencing the extinction coefficient of the foams under study. The experimental results agreed well with the Glicksman model. Moreover, the total thermal conductivity was calculated in terms of the Rosseland equation with an accuracy of 5%. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1608–1617, 2005     

Friction and wear mechanisms of polyamide 66/high density polyethylene blends

Polyamide 66 (PA66)/high density polyethylene (HDPE) blends having miscible structure were produced by compatibilization of HDPE grafted with maleic anhydride (HDPE‐g‐MAH). Mechanical and tribological properties of blends in different compositions were tested. It was found that the polymer blends greatly improved the mechanical properties of PA66 and HDPE. Blending HDPE with PA66 significantly decreased the friction coefficient of PA66; the friction coefficients of blends with different compositions were almost the same and approximately equal to that of pure HDPE; the blends with 80 vol % PA66 exhibited the best wear resistance. The transfer films, counterpart surfaces, and wear debris formed during sliding were investigated by Scanning Electron Microscopy (SEM), and Differential Scanning Calorimetry (DSC) analysis was further carried out on wear debris. These investigations indicated that the thermal control of friction model is applicable to PA66/HDPE blend, that is the friction coefficient of blend is governed by the HDPE component, which possesses a lower softening point relative to the PA66 component in this system. The wear mechanism of PA66/HDPE blend transforms from PA66 to HDPE as the HDPE content increases. PA66, as the component with higher softening point, increases the hardness of blend, enhances the ability of blend to form a transfer film on the counterface, and inhibits the formation of larger belt‐like debris of HDPE, at the same time, the presence of self‐lubricating HDPE in the system decreases the friction coefficient and the frictional heat, all of these factors are favorable for the wear resistance of PA66/HDPE blend. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2514–2523, 2005     

Polyimides based on new diamines having pendant imide groups

New aromatic diamines were prepared in two steps from 4,5‐dichlorophthalic anhydride and primary amines. The resulting 4,5‐dichlorophthalimide was reacted with 4‐mercaptoaniline, so that the chloroatoms were substituted by the mercapto groups (via the sulfide anions). The new diamines were polycondensed either with the diphenyl ether 3,3′,4,4′‐tetracarboxylic anhydride or with bicyclooctane tetracarboxylic anhydride. These polycondensations were conducted in boiling m‐cresol with azeotropic removal of water. The isolated polyimides were characterized by viscosity measurement, IR‐spectroscopy, elemental analyses, and MALDI‐TOF mass spectrometry. The mass spectra evidenced a high content of cyclic polyimides, indicating nearly perfect reaction conditions. The mass spectra also proved the formation of copolymers containing one diamine with a trialkylamine group in the side chain. High glass transition temperatures but a low crystallization tendency were found by DSC measurements. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6272–6281, 2005     

Modification of multiwall carbon nanotubes via soap‐free emulsion polymerization of acrylonitrile

A novel method for the synthesis of polyacrylonitrile (PAN)‐coated multiwall carbon nanotubes (MWCNTs) via a simple soap‐free emulsion polymerization is presented for the first time. The polymerization was initiated with conventional anionic ammonium persulfate (APS) at 65 °C. The modification of PAN on MWCNT surfaces was confirmed by Fourier‐transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectra (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy. It is found that all the surfaces of the MWCNTs were coated by PAN chains, and the PAN coating thickness could be controlled by simply adjusting the polymerization time. The obtained PAN‐coated MWCNTs could be well dispersed in water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2057–2062, 2010     

d-Poly(lactide) and LHRH decapeptide stereointeractions investigated by vibrational spectroscopy

The interactions between poly(d-lactic acid) (PDLA) and l-configured leuprolide (LHRH) to form heterocomplexes were investigated by a combination of infrared (IR), Raman and near infrared spectroscopy (NIR). It was found that an α crystal with 10₃ helical conformation of PDLA is formed in the PDLA/LHRH heterocomplexes with various LHRH loadings, whereas the secondary structures of LHRH in these heterocompelexes are greatly affected by the blend ratio of LHRH and PDLA. Based on the analysis of IR, Raman and NIR spectra of the various heterocomplexes, it is suggested that stereoselective Van der Waals interactions, consisting of interwined α helices of PDLA and LHRH, is responsible for the driving force of PDLA and LHRH stereocomplexation. To clarify the solid structure and the potential interaction in these heterocomplexes with various LHRH loadings, temperature-dependent IR spectral measurements were also employed. On the basis of the results presented, a model for the PDLA and LHRH stereointeraction process was proposed.     

The effect of compatibilization on the dynamic properties of polypropylene/nylon‐6 blends studied by broad band dielectric spectroscopy

Polypropylene (PP) and polyamide‐6 (Ny‐6) blends with a 70/30 composition have been studied by broadband dielectric spectroscopy. The unmodified blends are immiscible, and 10% of PP functionalized with maleic anhydride was added as a compatibilizer. The influence of the compatibilizer on the water sorption and on the molecular dynamics of the Ny‐6 phase is followed by the changes induced in the dielectric loss spectra of these blends in both wet and dry states. The shortest range motions are unaffected by the compatibilizer in the dry state, but a higher water sorption is observed in the unmodified blend. Higher activation energies are found for the β relaxation in the dry blends than for the Ny‐6 homopolymer, showing the existence of constraints on these longer scale motions. During increasing temperature experiments, two segmental modes are recorded, the lower temperature mode corresponding to the plasticized material; as the temperature is raised, a second cooperative mode is found, originating in the dry Ny‐6 amorphous phase, rigidized by the loss of moisture. The comparison of the dielectric strengths of the modes shows that the unmodified blend absorbs more water than the compatibilized blend. The segmental dynamics are unaffected by compatibilization. At high temperatures, the high temperature tail of the segmental mode is much higher in the absence of the compatibilizer. The contribution of a peak due to interfacial polarization is lowered by the presence of the compatibilizer, which makes the interface more diffuse and the trapping of free carriers less effective. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1408–1420, 2005     

Miscibility behavior and hydrogen bonding in blends of poly(vinyl phenyl ketone hydrogenated) and poly(2‐ethyl‐2‐oxazoline)

The miscibility behavior of poly(2‐ethyl‐2‐oxazoline) (PEOx)/poly(vinyl phenyl ketone hydrogenated) (PVPhKH) blends was studied for the entire range of compositions. Differential scanning calorimetry and thermomechanical analysis measurements showed that all the PEOx/PVPhKH blends studied had a single glass‐transition temperature (T_g). The natural tendency of PVPhKH to self‐associate through hydrogen bonding was modified by the presence of PEOx. Partial IR spectra of these blends suggested that amide groups in PEOx and hydroxyl groups in PVPhKH interacted through hydrogen bonding. This physical interaction had a positive influence on the phase behavior of PEOx/PVPhKH blends. The Kwei equation for T_g as a function of the blend composition was satisfactorily used to describe the experimental data. Pure‐component pressure–volume–temperature data were also reported for both PEOx and PVPhKH. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 636–645, 2004     

Thermal behavior and intermolecular interactions in blends of poly(3‐hydroxybutyrate) and maleated poly(3‐hydroxybutyrate) with chitosan

The thermal behavior and intermolecular interactions of blends of poly(3‐hydroxybutyrate) (PHB) and maleated PHB with chitosan were studied with differential scanning calorimetry, Fourier transform infrared (FTIR), wide‐angle X‐ray diffraction (WAXD), and X‐ray photoelectron spectroscopy (XPS). The differences in the two blend systems with respect to their thermal behavior and intermolecular interactions were investigated. The melting temperatures, melting enthalpies, and crystallinities of the two blend systems gradually decreased as the chitosan content in the blends increased. Compared with that of the PHB component with the same composition, the crystallization of the maleated PHB component was more intensively suppressed by the chitosan component in the blends because of the rigid chitosan molecular chains and the intermolecular hydrogen bonds between the components. FTIR, WAXD, and XPS showed that the intermolecular hydrogen bonds in the blends were caused by the carbonyls of PHB or maleated PHB and chitosan aminos, and their existence depended on the compositions of the blends. The introduction of maleic anhydride groups onto PHB chains promoted intermolecular interactions between the maleated PHB and chitosan components. In addition, the intermolecular interactions disturbed the original crystal structures of the PHB, maleated PHB, and chitosan components; this was further proven by WAXD results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 35–47, 2005     

Miscible blend dynamics and the length scale of local compositions

We consider the influence of a local, or effective, composition on dynamics in the miscible polymer blend PEO/PMMA. Quasielastic neutron scattering in combination with deuterium labeling is employed to determine characteristic relaxation times of the PEO component over spatial scales from 3 to 10 Å. Information about the distribution of relaxation times is obtained indirectly from the stretching parameters in a stretched exponential fit. We examine the behavior of these parameters with spatial scale and temperature, finding that their variation supports a distribution of PEO mobility in the blend which is far wider than pure PEO and narrows with decreasing temperature for small spatial scales. This is linked to the concept of local compositions defined over varying spatial scales, and indicates that the concept of a local composition, linked to PEO dynamics, is important in this system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2914–2923, 2005     

Thermal and spectroscopy studies on ternary miscibility and phase behavior in blends comprising poly(4‐vinyl phenol) and two aryl polyesters

Thermal analysis and Fourier transform infrared spectroscopy characterizations were performed on three ternary blend systems that comprise poly(4‐vinyl phenol) (PVPh) and any two of the three homologous aryl polyesters [poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT)]. Although PVPh is miscible with any one of the polyesters in forming a binary blend system, miscibility in ternary systems by introducing one more polymer of different structures to the blend system is not always expected. However, this study concludes that miscibility does exist in all these three ternary blends of all compositions investigated. Reasons and factors for such behavior were probed. Quantitative interactions in the ternary blend system were also estimated. The overall interaction energy density (B) by analysis of melting point depression for the PBT/PVPh/PET ternary blend system led to a negative value (B = −5.74 cal/cm³). Similarly, T_g‐composition analyses were performed on two other ternary blend systems, PET/PVPh/PTT and PTT/PVPh/PBT. Comparison of the qualitative results showed that the interaction energy densities in the other two ternary blend systems are similarly negative and comparable to the PBT/PVPh/PET ternary blend system. The Fourier transform infrared spectroscopy results also support the qualitative findings among these three ternary blend systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1339–1350, 2006     

Formation of conjugated polyene and polyyne structure by KrF excimer laser-induced dehydrochlorination on polyvinylidenechloride film

The surface dehydrochlorination of poly(vinyldenchloride) film was performed to produce a conjugated polyyne and polyene structures by photo-irradiation with a KrF excimer laser at 248 nm in a vacuum chamber. The reaction was confirmed by detection of HCl with a mass spectrometer and by measurement of chlorine content on the film with X-ray photoelectron spectroscopy. UV-visible absorption spectroscopy for the laser-treated film showed the formation of new broad absorption bands in the visible and near IR region, indicating that sequential dehydrochlorination induced the formation of conjugated carbon multiple bonds in the polymer chain. Its conjugation number is estimated to be 30 for a triple bond and 10–25 for a double bond from the peak positions on the Raman spectrum of the film. ESR spectra of laser-irradiated PVDC powder also showed long-lived radicals having a narrow band width (ΔH_pp = 0.15 mT), suggesting that the radicals were delocalized on the conjugated bonds. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2483–2487, 1998     

过渡金属表面α-吡啶基的振动光谱学判据

基于簇模型采用密度泛函理论在B3LYP/6-311+G^**/LANL2DZ(metal)基组水平上计算了吡啶及α-吡啶基吸附于Pt、Pd、Rh、Ni四种金属表面的红外和拉曼光谱. 通过详细地分析和比较计算结果与文献报道的实验谱图, 提出了以N端吸附的吡啶分子和α-吡啶基这两种表面物种各自存在的谱学判据. 计算结果表明在以上四种金属表面, α-吡啶基的拉曼活性比吡啶的小, 而特征谱峰的红外强度与吡啶相当. 该结果表明红外光谱是检测金属表面α-吡啶基的有效手段, 也解释了采用表面增强拉曼光谱和红外光谱研究吡啶吸附在金属表面得出不同结构的原因.     

Novel biodegradable poly(butylene succinate)/poly(ethylene oxide) blend film with compositional and spherulite‐size gradients

Biodegradable poly(butylene succinate) (PBS)/poly(ethylene oxide) (PEO) polymer blend film with compositional gradient in the film thickness direction was prepared using a method of interdiffusion across the interface between the PBS and PEO layers at a temperature above the melting points of both the component polymers. The miscibility between PBS and PEO was confirmed by observation of the glass transition temperature by differential scanning calorimetry. The compositional gradient structure of PBS/PEO was characterized by microscopic mapping measurement of Fourier transform infrared spectra and dynamic mechanical thermal analysis. Furthermore, a new method for confirming the crystalline/crystalline compositional gradient structure through observing the crystallization behavior by POM (polarized optical microscopy) was put forward. A continuous gradient of the spherulite size along the film thickness direction was succeessfully generated in the PBS/PEO blend film. The compositional gradient blend was found to have significantly improved physical properties that cannot be realized for pure PBS, pure PEO, and even their homogeneous miscible blend system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 368–377, 2005     

Influence of different laser irradiation methods on determination of composition content in polypropylene/low-density polyethylene blends using Raman spectroscopy

Sample movement makes a difference to raw Raman spectra and determination of composition content using Raman spectroscopy. Therefore, it is necessary to have further studies in this aspect. In this paper, different laser irradiation methods were investigated for determination of composition content in polypropylene (PP)/low-density polyethylene (LDPE) blends using Raman spectroscopy. Raw Raman spectra of PP sample were firstly collected using different laser irradiation methods. It was shown that the relative standard deviations (RSD) of PP sample under circle irradiation were ten times bigger than that under point irradiation at the little sacrifice of signal-to-noise ratio (SNR). In other words, rotating (or moving) PP sample during Raman spectra collection could signally improve sample representation. Owing to this, in combined with partial least squares (PLS), Raman quantitative analysis of PP concentration in PP/LDPE blends were performed by different laser irradiation methods. The results validated that blend samples with rotation during Raman measurement led to lower prediction errors in prediction of PP concentration. The best root-mean-square error of prediction (RMSEP) and coefficient of determination (R²) that were obtained for PP were respectively 2.10% and 0.9884.