Surface plasma treatment effects on the molecular structure at polyimide/air and buried polyimide/epoxy interfaces

Polyimides are widely used as chip passivation layers and organic substrates in microelectronic packaging. Plasma treatment has been used to enhance the interfacial properties of polyimides, but its molecularmechanism is not clear. In this research, the effects of polyimide surface plasma treatment on the molecular structures at corresponding polyimide/air and buried polyimide/epoxy interfaces were investigated in situ using sum frequency generation (SFG) vibrational spectroscopy. SFG results show that the polyimide backbone molecular structure was different at polyimide/air and polyimide/epoxy interfaces before and after plasma treatment. The different molecular structures at each interface indicate that structural reordering of the polyimide backbone occurred as a result of plasma treatment and contact with the epoxy adhesive. Furthermore, quantitative orientation analysis indicated that plasma treatment of polyimide surfaces altered the twist angle of the polyimide backbone at corresponding buried polyimide/epoxy interfaces. These SFG results indicate that plasma treatment of polymer surfaces can alter the molecular structure at corresponding polymer/air and buried polymer interfaces.     

Surface structures and properties of polystyrene/poly(methyl methacrylate) blends and copolymers

Sum frequency generation (SFG) vibrational spectroscopy has been applied to study the molecular surface structures of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends and the copolymer between PS and PMMA (PS-co-PMMA) in air, supplemented by atomic force microscopy (AFM) and contact angle goniometer. Both the blend and the copolymer have equal weight amounts of the two components. SFG results show that both components, PS and PMMA, can segregate to the surface of the blend and the copolymer before annealing, although PMMA has a slightly higher surface tension. Upon annealing both SFG results and contact angle measurements indicate that the PS segregates to the surface of the PS/PMMA blend more but no change occurs on the PS-co-PMMA surface. AFM images show that the copolymer surface is flat but the 1:1 PS/PMMA blend has a rougher surface with island like domains present. The annealing effect on the blend surface morphology has also been investigated. We collected amide SFG signals from interfacial fibrinogen molecules at the copolymer or blend/protein solution interfaces as a function of time. Different time-dependent SFG signal changes have been observed, showing that different surfaces of the blend and the copolymer mediate fibrinogen adsorption behavior differently.     

Detection of tethered biocide moiety segregation to silicone surface using sum frequency generation vibrational spectroscopy

Polymer surface properties are controlled by the molecular surface structures. Sum frequency generation (SFG) vibrational spectroscopy has been demonstrated to be a powerful technique to study polymer surface structures at the molecular level in different chemical environments. In this research, SFG has been used to study the surface segregation of biocide moieties derived from triclosan (TCS) and tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride (C-14 QAS) that have been covalently bound to a poly(dimethylsiloxane) (PDMS) matrix. PDMS materials are being developed as coatings to control biofouling. This SFG study indicated that TCS-moieties segregate to the surface when the bulk concentration of TCS-moieties exceeds 8.75% by weight. Surface segregation of C-14 QAS moieties was detected after 5% by weight incorporation into a PDMS matrix. SFG results were found to correlate well with antifouling activity, providing a molecular interpretation of such results. This research showed that SFG can aid in the development of coatings for controlling biofouling by elucidating the chemical structure of the coating surface.     

Probing molecular-level surface structures of polyethersulfone/pluronic F127 blends using sum-frequency generation vibrational spectroscopy

We blended Pluronic F127 into polyethersulfone (PES) to improve surface properties of PES, which has been extensively used in biomaterial and other applications. The molecular surface structures of PES/Pluronic F127 blends have been investigated by sum-frequency generation (SFG) vibrational spectroscopy. The molecular orientation of surface functional groups of PES changed significantly when blended with a small amount of Pluornic F127. Pluronic F127 on the blend surface also exhibited different features upon contacting with water. The entanglement of PES chains with Pluronic F127 molecules rendered the blends with long-term surface stability in water in contrast to the situation where a layer of Pluronic F127 adsorbed on the PES surface. Atomic force microscopy (AFM) and quartz crystal microbalance (QCM) measurements were included to determine the relative amount of protein that adsorbed to the blend surfaces. The results showed a decreased protein adsorption amount with increasing Pluronic F127 bulk concentration. The correlations between polymer surface properties and detailed molecular structures obtained by SFG would provide insight into the designing and developing of biomedical polymers and functional membranes with improved fouling-resistant properties.     

Entropically mediated polyolefin blend segregation at buried sapphire and air interfaces investigated by infrared-visible sum frequency generation vibrational spectroscopy

The segregation behavior of binary polymer blends at hydrophilic solid sapphire and air interfaces was investigated by infrared-visible sum frequency generation (SFG) vibrational spectroscopy. SFG spectra were collected from a bulk miscible blend consisting of identical molecular weight (approximately 54,000) and similar surface free energy (29-35 dyn/cm) components of atactic polypropylene (aPP) and aspecific poly(ethylene-co-propylene) rubber (aEPR). Characteristic CH resonances of the blend were contrasted with those of the individual components at both buried (sapphire/polymer) and free (air/polymer) interfaces. Preferential segregation of the aPP component was observed after annealing at both air/polymer and sapphire/polymer interfaces. SFG spectra revealed ordering of the polymer backbone segments with the methylene (CH2) groups perpendicular to the surface at the sapphire interface and the methyl (CH3) groups upright at the air interface. The SFG results indicate that the surface composition can be determined from the peak intensities that are characteristic of each component and that conformational entropy played a likely role in surface segregation. aPP occupied a smaller free volume at the surface because of a statistically smaller segment length (aPP is more flexible and has a shorter length). In addition, the high density of the ordered CH3 side branches enhanced the surface activity by allowing the long-chain backbone segments of aPP to order at the surface.     

Kinetics of thermal degradation of poly(vinyl chloride)

Extensively studied thermal degradation of polyvinyl chloride (PVC) occurs with formation of free hydrogen chloride and conjugated double bonds absorbing light in visible region. Thermogravimetric monitoring of PVC blends degradation kinetics by the loss of HCl is often complicated by evaporation and degradation of plasticizers and additives. Spectroscopic PVC degradation kinetics monitoring by absorbance of forming conjugated polyenes is specific and should not be affected by plasticizers loss. The kinetics of isothermal degradation monitored by thermal gravimetric analysis in real time was compared with batch data obtained by UV/Visible absorption spectroscopy. Effects of plasticizer on kinetics of polyene formation were examined. Thermal degradation of PVC films plasticized with di-(2-ethylhexyl) phthalate (DEHP) and 1,2,4-benzenedicarboxylic acid, tri-(3-ethylhexyl) ester (TOTM) was monitored by conjugated double bonds light absorption at 350 nm at 160, 180, and 200 °C. Plasticizer-free PVC powder degradation kinetics and that of plasticized films were also obtained thermogravimetrically at temperatures ranging from 160 to 220 °C. Plasticizer-free PVC powder degradation and spectroscopically monitored degradation of plasticized PVC films occurred with the same apparent activation energy of ≈150 kJ mol⁻¹. No difference in degradation kinetics of films plasticized with DEHP and TOTM was detected.     

Surface restructuring behavior of various types of poly(dimethylsiloxane) in water detected by SFG

Surface structures of several different poly(dimethylsiloxane) (PDMS) materials, tetraethoxysilane-cured hydroxy-terminated PDMS (TEOS-PDMS), platinum-cured vinyl-terminated PDMS (Pt-PDMS), platinum-cured vinyl-terminated poly(diphenylsiloxane)-co-poly(dimethylsiloxane) (PDPS-co-PDMS), and PDMS-co-polystyrene (PDMS-co-PS) copolymer in air and water have been investigated by sum frequency generation (SFG) vibrational spectroscopy. The SFG spectra collected from all PDMS surfaces in both air and water are dominated by methyl group stretches, indicating that all the surfaces are mainly covered by methyl groups. Other than surface-dominating methyl groups, some -Si-CH2-CH2- moieties on the Pt-PDMS surface have also been detected in air, which are present at cross-linking points. Information about the average orientation angle and angle distribution of the methyl groups on the PDMS surface has been evaluated. Surface restructuring of the methyl groups has been observed for all PDMS surfaces in water. Upon contacting water, the methyl groups on all PDMS surfaces tilt more toward the surface. The detailed restructuring behaviors of several PDMS surfaces in water and the effects of molecular weight on restructuring behaviors have been investigated. For comparison, in addition to air and water, surface structures of PDMS materials mentioned above in a nonpolar solvent, FC-75, have also been studied. By comparing the different response of phenyl groups to water on both PDPS-co-PDMS and PS-co-PDMS surfaces, we have demonstrated how the restructuring behaviors of surface phenyl groups are affected by the structural flexibility of the molecular chains where they are attached.     

Influence of polyesterurethane plasticizer on the kinetics of poly(vinyl chloride) decomposition process

Poly(vinyl chloride) (PVC), plasticized by di(2-ethylhexyl) phthalate (DEHP), medium molecular mass polyesterurethane (PU) or by both plasticizers, was thermally degraded under dynamic thermogravimetric conditions and the kinetics of decomposition was studied by isoconversional methods and by non-linear regression. It has been found that the initial decomposition temperature is higher for PVC plasticized with PU, as compared with PVC plasticized with di(2-ethylhexyl) phthalate (DEHP) or plasticized with PU/DEHP, and thermal degradation shows features of a multi-step complex process. Application of polymeric plasticizer leads to the increase and a 'smoothing' effect in the course of energy of activation and pre-exponential factor at the initial stage of decomposition indicating thus the hindered migration of medium molecular mass compound from PVC matrix (in comparison with PVC containing monomeric DEHP) due to steric hindrances as well as due to specific interactions between C=O and Cl groups along the macrochains. Kinetic model function of the decomposition process of PVC/DEHP and PVC/DEHP/PU blends was found to be a two-stage autocatalyzed reaction of n^th order; autocatalytic effect is associated most likely with the role of HCl formed during PVC decomposition. For PVC/PU blend best fit was found by non-linear regression for a two-stage scheme in which first stage was Prout-Tompkins model and the second was autocatalytical model of n^th order - the first one involves particle disintegration, which was promoted by product generation at branching PVC 'pseudo-crystals' nuclei, thus exposing more surface on which decomposition reaction proceeds.     

Poly(?-caprolactone)-based ‘green’ plasticizers for poly(vinyl choride)

A series of proposed plasticizers for poly(vinyl chloride) (PVC), based on poly(?-caprolactone) (PCL) with octanoate and benzoate-terminal groups, were synthesized with various microstructures and molecular weights (MW) and tested for biodegradability as well as for mechanical performance, and leaching resistance in blends with PVC. The plasticization efficiency of each was characterized by measuring the glass transition temperature (T_g) and tensile properties of PCL/PVC blends. The PCL-octanoate plasticizers demonstrated plasticization efficiency similar to di(ethylhexyl) phthalate (DEHP) with the same plasticizer loading. PCL-benzoate/PVC blends had much higher T_gs (∼20 °C higher) compared to PCL-octanoate/PVC and DEHP/PVC blends. Yield stresses were about two times higher for PCL-benzoate/PVC blends compared to PCL-octanoate/PVC and DEHP/PVC blends, reflecting the stiffer nature of such blends. Biodegradation was rapid for all PCL-octanoates, with the exception of linear PCL-octanoates with arm molecular weights >10³ g mol⁻¹. Biodegradation rates of PCLs by Rhodococcus rhodocrous were not affected by microstructure for the range of PCL topologies studied (linear versus three or four arms) but were slower for PCLs made from commercial PCL-diols that had a central ether linkage due to the initiator used to make these compounds. Leaching resistance was higher as PCL molecular weight increased and, for pairs of comparable sized species, significantly less PCL-benzoate leached out compared to the PCL-octanoate. For the range of PCL topologies studied, the number of arms did not significantly affect leaching resistance. In summary, both the end group and the molecular weight influenced the leaching resistance of the PCL. PCL-octanoates were comparable plasticizers to DEHP in terms of the mechanical properties examined, and were rapidly degraded by a common soil microorganism.     

Adsorption of 1- and 2-butylimidazoles at the copper/air and steel/air interfaces studied by sum frequency generation vibrational spectroscopy

The structure of thin films of 1- and 2-butylimidazoles adsorbed on copper and steel surfaces under air was examined using sum frequency generation (SFG) vibrational spectroscopy in the ppp and ssp polarizations. Additionally, the SFG spectra of both isomers were recorded at 55 °C at the liquid imidazole/air interface for reference. Complementary bulk infrared, reflection-absorption infrared spectroscopy (RAIRS), and Raman spectra of both imidazoles were recorded for assignment purposes. The SFG spectra in the C-H stretching region at the liquid/air interface are dominated by resonances from the methyl end group of the butyl side chain of the imidazoles, indicating that they are aligned parallel or closely parallel to the surface normal. These are also the most prominent features in the SFG spectra on copper and steel. In addition, both the ppp and ssp spectra on copper show resonances from the C-H stretching modes of the imidazole ring for both isomers. The ring C-H resonances are completely absent from the spectra on steel and at the liquid/air interface. The relative intensities of the SFG spectra can be interpreted as showing that, on copper, under air, both butylimidazoles are adsorbed with their butyl side chains perpendicular to the interface and with the ring significantly inclined away from the surface plane and toward the surface normal. The SFG spectra of both imidazoles on steel indicate an orientation where the imidazole rings are parallel or nearly parallel to the surface. The weak C-H resonances from the ring at the liquid/air interface suggest that the tilt angle of the ring from the surface normal at this interface is significantly greater than it is on copper.     

Molecular packing of lysozyme,fibrinogen, and bovine serum albumin on hydrophilic and hydrophobic surfaces studied by infrared-visible sum frequency generation and fluorescence microscopy

Infrared-visible sum frequency generation (SFG) vibrational spectroscopy, in combination with fluorescence microscopy, was employed to investigate the surface structure of lysozyme, fibrinogen, and bovine serum albumin (BSA) adsorbed on hydrophilic silica and hydrophobic polystyrene as a function of protein concentration. Fluorescence microscopy shows that the relative amounts of protein adsorbed on hydrophilic and hydrophobic surfaces increase in proportion with the concentration of protein solutions. For a given bulk protein concentration, a larger amount of protein is adsorbed on hydrophobic polystyrene surfaces compared to hydrophilic silica surfaces. While lysozyme molecules adsorbed on silica surfaces yield relatively similar SFG spectra, regardless of the surface concentration, SFG spectra of fibrinogen and BSA adsorbed on silica surfaces exhibit concentration-dependent signal intensities and peak shapes. Quantitative SFG data analysis reveals that methyl groups in lysozyme adsorbed on hydrophilic surfaces show a concentration-independent orientation. However, methyl groups in BSA and fibrinogen become less tilted with respect to the surface normal with increasing protein concentration at the surface. On hydrophobic polystyrene surfaces, all proteins yield similar SFG spectra, which are different from those on hydrophilic surfaces. Although more protein molecules are present on hydrophobic surfaces, lower SFG signal intensity is observed, indicating that methyl groups in adsorbed proteins are more randomly oriented as compared to those on hydrophilic surfaces. SFG data also shows that the orientation and ordering of phenyl rings in the polystyrene surface is affected by protein adsorption, depending on the amount and type of proteins.     

Designing anti-migration furan-based plasticizers and their plasticization properties in poly (vinyl chloride) blends

The use of bio-based plasticizers with low toxicity and good compatibility with polyvinyl chloride (PVC) has attracted more attention in the recent years. With bio-based 2, 5-furandicarboxylic acid (FDCA) and butyl oligo-glycol ethers as raw materials, three liquid furan-based plasticizers of di(butyl glycol) furan-2,5-dicarboxylate, di(butyldiglycol) furan-2,5-dicarboxylate and di(butyltriglycol) furan-2,5-dicarboxylate were synthesized by direct esterification. The chemical structure of three plasticizers was characterized with FTIR, ¹H NMR and ¹³C NMR. From DMA measurement, the glass transition temperature (T_g) of the plasticized PVC was decreased gradually when furan-based plasticizers were added to PVC formulation from 30 up to 50 phr. Due to lots of ether bonds in furan-based plasticizers, they expressed over two-fold lower migration in organic solvent compared with the traditional plasticizer diethylhexyl phthalate (DEHP). Through the characterization of elongation at break, hardness and thermal stability, furan-based plasticizers presented the same plasticization properties as DEHP, and had potential industrial application prospects.     

Studying nanoparticle-induced structural changes within fatty acid multilayer films using sum frequency generation vibrational spectroscopy

The nonlinear optical technique of sum frequency generation (SFG) vibrational spectroscopy has been used for the first time to study CdS nanoparticle/arachidic acid multilayer structures. Using a combination of per-deuterated and per-protonated arachidic acid, it is possible to study individual layers anywhere within the film, buried or on the surface. Before reaction with H2S all layers are highly ordered, but after the reaction the layers become highly disordered, except for the surface layer, which remains well ordered. This sheds new light on the structure and stability of these films and shows that SFG can provide unique structural information.     

Molecular orientation of asphaltenes and PAH model compounds in Langmuir-Blodgett films using sum frequency generation spectroscopy

Asphaltenes are an important class of compounds in crude oil whose surface activity is important for establishing reservoir rock wettability which impacts reservoir drainage. While many phenomenological interfacial studies with crude oils and asphaltenes have been reported, there is very little known about the molecular level interactions between asphaltenes and mineral surfaces. In this study, we analyze Langmuir-Blodgett films of asphaltenes and related model compounds with sum frequency generation (SFG) vibrational spectroscopy. In SFG, the polarization of the input (vis, IR) and output (SFG) beams can be varied, which allows the orientation of different functional groups at the interface to be determined. SFG clearly indicates that asphaltene polycyclic aromatic hydrocarbons (PAHs) are highly oriented in the plane of the interface and that the peripheral alkanes are transverse to the interface. In contrast, model compounds with oxygen functionality have PAHs oriented transverse to the interface. Computational quantum chemistry is used to support corresponding band assignments, enabling robust determination of functional group orientations.     

Carbon monoxide adsorption and oxidation on monolayer films of cubic platinum nanoparticles investigated by infrared-visible sum frequency generation vibrational spectroscopy

The adsorption and oxidation of CO on monolayer films of cubic Pt nanoparticles synthesized by a modified solution-phase polyol process were examined by sum frequency generation (SFG) vibrational spectroscopy in total internal reflection (TIR) geometry. Extremely low incident laser power (approximately 5 microJ/pulse of infrared) yields sufficient SFG intensity in TIR geometry and reduces destructive interference. Because TIR-SFG spectroscopy does not require correction for bulk gas absorption, CO spectra can be collected over a wide pressure range (<1 mTorr up to 700 Torr). Poly(vinylpyrrolidone)-capped Pt nanoparticles deposited on single-crystal sapphire were monitored under high-pressure reaction conditions in a combined spectroscopy-catalytic reactor cell. The effect of the capping polymer on the position and intensity of the CO peak was studied before and after low-temperature calcination. The polymer decreased the amount of CO adsorption and caused a slight red-shift of the atop CO band relative to a surface treated in oxygen at 373 K. Oxidation rates were determined by measuring the intensity of the atop CO peak as a function of time in the presence of flowing oxygen. The activation energy (approximately 19.8 kcal/mol) determined from the SFG data is close to that obtained from gas chromatography (GC) measurements of CO oxidation rates at different temperatures. The SFG and GC results are in good agreement with published data for Pt(100) surfaces.     

Molecular restructuring at poly(n-butyl methacrylate) and poly(methyl methacrylate) surfaces due to compression by a sapphire prism studied by infrared-visible sum frequency generation vibrational spectroscopy

Infrared-visible sum frequency generation (SFG) vibrational spectroscopy, performed in visible wavelength total internal reflection (TIR) geometry, was used to determine the molecular structures of poly(n-butyl methacrylate) (PBMA) and poly(methyl methacrylate) (PMMA) surfaces in air and in contact with a smooth sapphire surface with and without the application of pressure. C-H vibrational resonances were probed optically to nondestructively examine the buried polymer/sapphire interfaces and obtain information about the molecular orientation in situ. These findings are contrasted with those of the same polymers cast from a toluene solution directly on the sapphire prism surface and annealed. Compared to polymer surface conformation in air, the SFG spectra of the deformed (compressed) PBMA at the sapphire interface illustrate that the ester butyl side chain restructures and tilts away from the surface normal. However, the molecular conformation in the similarly deformed PMMA at the sapphire interface is identical to that obtained in air, which is dominated by the upright-oriented ester methyl side chains. For PBMA and PMMA spin cast on sapphire and annealed, the surface structure of the undeformed PBMA at the sapphire interface is identical to that of the deformed PBMA at the sapphire interface, while the PMMA conformation is different and shows alpha-methyl group ordering. Since the glass transition temperature of PBMA is below room temperature, the rubbery state of PBMA demonstrates a melt-like behavior, evidenced by the fact that PBMA is in conformation chemical equilibrium at the sapphire surface even under compression. Due to the high glass transition temperature of PMMA, compression freezes PMMA in a metastable state, revealed by the restructured molecular conformation when annealed against the sapphire surface. The results of this study demonstrate that structural changes at buried polymer surfaces due to the application of contact pressure can be detected in situ by TIR-SFG vibrational spectroscopy.     

SURFACE REARRANGEMENTS OF OXYGEN PLASMA TREATED POLYSTYRENE： SURFACE DYNAMICS AND HUMIDITY EFFECT

The time evolution of oxygen plasma treated polystyrene(PS)surfaces was investigated upon storing them in theair under controlled humidity conditions.The methods of water contact angle,X-ray photoelectron spectroscopy(XPS),sumfrequency generation(SFG)vibrational spectroscopy,and atomic force microscopy(AFM)were used to infer the surfaceproperties and structure.Chemical groups containing oxygen were formed on the PS surface with the plasma treatment,demonstrated by water contact angle and XPS.The surface polarity decayed markedly on time,as assessed by steady increasein the water contact angle as a function of storage time,from zero to around 60°.The observed decay is interpreted as arisingfrom surface rearrangement processes to burying polar groups away from the uppermost layer of the surfaces,which is incontact with air.On the other hand,XPS results show that the chemical composition in the first 3 nm surface layer isunaffected by the surface aging,and the depth profile of oxygen is essentially the same with time.A possible change of PSsurface roughness was examined by AFM,and it showed that the increase of water contact angle during surface aging couldnot be attributed to surface roughness.Thus,it is concluded that surface aging is attributable to surface reorganization andthe motion of oxygen containing groups is confined within the XPS probing depth.SFG spectroscopy,which is intrinsicallyinterface-specific,was used to detect the chemical structure of PS surface at the molecular level after various aging times.The results are interpreted as follows.During the aging of the plasma treated PS surfaces,the oxygen containing groupsundergo reorientation processes toward the polymer bulk and/or parallel to the surface,while the CH_2 moiety stands up onthe PS surface.Our results indicate that the surface configuration changes do not require large length scale segmentalmotions or migration of macromolecules.Motions that are responsible for surface configuration changes could be relativelysmall rotational motions.The aging behaviors under different relative humidity conditions were shown to be similar from18% to 91%,whereas the kinetics of surface polarity decays were faster in higher relative humidity.Here,the surfacerearrangement of polystyrene films that were previously treated by oxygen plasma and aged,and was investigated in terms ofcontact angle after the water immersion.The contact angles of the water-immersed samples were found to change andapproach the initial values before the immersion asymptotically.     

邻苯二甲酸二(2-乙基)己酯和偏苯三酸三辛酯在临床不同药液中溶出量的比较

聚氯乙烯(PVC)材质的医疗器械产品中需要加入增塑剂以改善柔韧性,目前最常用的增塑剂是邻苯二甲酸二(2-乙基)己酯(DEHP)和偏苯三酸三辛酯(TOTM)。本文考察了PVC一次性使用输液器产品在脂溶性药液(紫杉醇注射液)、肠外营养液(脂肪乳)、酸性药液(左氧氟沙星,pH 3.0~5.0)和碱性药液(呋塞米,pH 8.0~9.0)中的DEHP和TOTM溶出量,并进行对比分析。先建立了一种高效液相色谱-紫外检测(HPLC-UV)方法测定增塑剂的溶出量,并利用该方法对增塑剂的溶出量进行了分析。实验结果表明,增塑剂在不同药液中均有一定的溶出情况,其中紫杉醇注射液对增塑剂的溶出量要高于脂肪乳,并远高于左氧氟沙星和呋塞米注射液。通过对比DEHP和TOTM的溶出量可以看出,在相同的浸提条件下,TOTM的溶出量远低于DEHP的溶出量。利用紫杉醇注射液浸提24 h,PVC输液器产品DEHP的溶出量为21.14 mg,而TOTM的溶出量仅为0.078 mg。DEHP的溶出量为TOTM溶出量的270倍。因此,TOTM具有的较好耐迁移性,是一种潜在的DEHP替代增塑剂。     

A Theoretical Investigation of Surface‐enhanced Sum‐frequency Generation

Following the surface enhanced Raman scattering (SERS), we shall investigate the possibility of observing surface‐enhanced sum‐frequency generation (SESFG), which refers to the transformation of ordinary vibrational SFG (i.e. singly resonant) into SESFG. Two mechanisms of SESFG will be studied; one is due to the transformation of singly‐resonant vibrational SFG into doubly resonant vibrational SFG (that is, both vibrationally resonant and Raman‐scattering resonant) and the other is due to the enhancement of the polarizability in addition to the original vibrational resonance in vibrational SFG.     

Plasticizer for poly(vinyl chloride) from cardanol as a renewable resource material

The present work is aimed to the preliminary analysis of the applicability of cardanol derivatives as renewable plasticizers for soft PVC. Two different plasticizers were studied, obtained by esterification of the cardanol hydroxyl group (cardanol acetate) and further epoxidation of the side chain double bonds (epoxidated cardanol acetate). Differential Scanning Calorimetry (DSC) was used to study the miscibility between PVC and cardanol derived plasticizers. The miscibility was correlated to the chemical structure of plasticizer by means of the Hansen solubility parameter analysis. Results obtained indicated that esterification of cardanol yields a partial miscibility with PVC, whereas esterification and subsequent epoxidation yield a complete miscibility with PVC. Therefore cardanol acetate, obtained by solvent-free esterification of cardanol, was used as a secondary plasticizer of PVC. Mechanical and rheological analysis showed that the cardanol acetate can partially replace DEHP in PVC formulation.