Complexes of starch polysaccharides and poly(ethylene co-acrylic acid): Structure and stability in solution

Chiroptical methods have been used to study the conformation and interactions of amylose and amylopectin with poly(ethylene co-acrylic acid) (EAA) in aqueous solution. These studies, along with X-ray diffraction and solid-state NMR data, show that amylose and EAA, as well as amylopectin and EAA, form helical V-type inclusion complexes when mixed in aqueous suspension. This structure apparently accounts for the partial compatibility observed in films containing starch and EAA. About 2/3 by weight of EAA does not interact with amylose and probably represents the ethylene-rich central core of the EAA micelle. EAA/amylose complexes in 10 mM NaOH were stable to temperatures > 90°C, whereas EAA/amylopectin complexes in the same solvent were largely disrupted at this temperature. Urea, at a concentration of 8 M, further destabilized both EAA/amylopectin and EAA/amylose complexes. Solutions with an alkaline pH (> 9.5) dispersed EAA optimally and allowed maximum complexing with amylose. At pH values > 13, the EAA/amylose complexes were weaker, most likely due to electrostatic repulsion between ionized hydroxyl groups of amylose and carboxyl groups of EAA.     

Structural characterization of new poly(ethylene oxide)-based alkaline solid polymer electrolytes

A new class of alkaline solid polymer electrolytes (SPEs) based on poly(ethylene oxide) (PEO), potassium hydroxide (KOH), and water was investigated. The structure of the SPEs was studied by differential scanning calorimetry, thermogravimetric analysis (TGA), X-ray diffraction, and optical microscopy techniques. The existence of a crystalline complex between PEO, KOH, and H₂O was evidenced for some compositions, depending on the O/K ratio. A possible structure was proposed, and a schematic phase diagram was established for this PEO–KOH–H₂O system. The first conductivity measurements also revealed the great interest of these systems, with conductivity values up to 10^-3 S/cm. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:601–607, 1997     

Preparation and characterization of poly(lactic acid)/poly(ethylene oxide) blend film: effects of poly(ethylene oxide) and poly(ethylene glycol) on the properties

Poly(lactic acid) (PLA) film plasticized with poly(ethylene oxide) (PEO) at various weight percentages (1–5 wt%) was prepared to improve the elongation, thus overcoming the inherent brittleness of the material. After optimization of the amount of PEO (4 wt%) through mechanical analysis, poly(ethylene glycol) (PEG), a well‐established plasticizer of PLA, was added (0.5–1.5 wt%) without hampering the transparency and tensile strength much, and again its amount was optimized (1 wt%). Neat PLA and PLA with the other components were solvent‐cast in the form of films using chloroform as a solvent. Improvement in elongation at break and reduction in tensile strength suggested a plasticizing effect of both PEO and PEG on PLA. Thermal and infrared data revealed that the addition of PEO induced β crystals in PLA. Scanning electron micrographs indicated a porous surface morphology of the blends. PEO alone in PLA exhibited the best optical clarity with higher percentage crystallinity, while PEG incorporation in PLA/PEO resulted in superior barrier properties. Also, the stability of the blends under a wide range of pH means prospective implementation of the films in packaging of food and non‐food‐grade products. © 2018 Society of Chemical Industry     

Structural characterization and luminescent properties of poly(p-phenylene vinylene) and poly(ethylene glycol) blends

The luminescent properties of poly(p-phenylenevinylene) (PPV) blending with poly (ethylene glycol) (PEG) were investigated in terms of their structural formation during sample preparation. The blended systems were prepared from an aqueous solution of water-soluble poly (xylylene tetrahydrothiophenium chloride) (PPV precursor) mixed with PEG, followed by heat treatment to remove the tetrahydrothiophene groups from the PPV precursor. Structural analysis showed that PEG could react with PPV precursor to form C-O-C linkage and carbonyl groups in PPV chains, interrupting their conjugated length as suggested by their Infrared, Raman and UV/vis spectroscopes. Wide angle X-ray scattering (WARS) of blended systems also showed that PPV in blends had less packing. As to luminescent properties, the UV/vis and photoluminescent (PL) spectra show that the energy gap needed to produce the excitons increased along with the increase of PL intensity when PPV was blended with PEG. Similar results were also found for the EL properties of ITO/polyblends/Al devices. The EL light emission from blends was blue-shifted (compared to PPV) with a rather low threshold electric field strength. The EL performance of polyblends was better than that of pure PPV. Among them, the PPV-50PEG showed the highest EL intensity. The improved EL efficiency was attributed to the dilution effect, interrupted conjugated length, and lower packing of PPV chains.     

Preparation and characterization of poly(ethylene carbonate)/poly(lactic acid) blends

Poly(ethylene carbonate)/poly(lactic acid) blends were successfully prepared by means of a solution film-casting method, and their physicochemical properties were investigated. PEC/PLA blends exhibit partial miscibility and are characterized by the interaction of the ester and carbonic ester groups. One such interaction is between partial charges in –C–O– in –O–C=O of PLA and the carbonyl –C=O of PEC. Another is between –C–O– in –O–C=O of PLA and –C–O– in –CH₂–O– of PEC. The value of T_g varies by more than 10 °C across the blends. PEC does not significantly influence the melting temperature of neat PLA, but non-spherical spherulites are formed in PEC-rich blends, whereas the spherulites are spherical with an average size of 30 μm in PLA-rich blends. Crystallization of PLA is influenced by the addition of flexible PEC and by the proportion of PLA in the blends. Interestingly, addition of at least 10 wt% PLA increased T_g, with a crystallinity, X_c of 47% and better thermal degradation properties, with the temperature at 5 wt% weight loss (T_d5) more than 30 °C higher than for neat PEC.     

Synthesis and characterization of complexes between poly(itaconic acid) and poly(ethylene glycol)

Summary Interpolymer complexes of poly(itaconic acid) and poly(ethylene glycol) (PIA/PEG) were prepared by two different procedures: simple mixing of preformed PIA and PEG and by polymerization of itaconic acid on poly(ethylene glycol) as a template. Complex formation was attributed to hydrogen bond formation between the carboxyl group of PIA and the ether group of PEG. The two types of complexes were characterized by viscometric measurements, thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy and adhesive force measurements. The results indicate that complexes prepared by template polymerization have a stronger hydrogen bonding and hence more ordered structure and better mucoadhesive properties.     

Kinetics of thermally induced solid state polycondensation of poly(ethylene terephthalate)

A diffusional model was established to study the kinetics of thermally-induced solid state polycondensation of poly(ethylene terephthalate). Diffusion through solid polymer is the rate controlling step when temperature is higher than 210°C and particle size is no smaller than 100 mesh. The activation energy is 30 Kcal/g mole. In polymerizing powders (20-200 mesh), the crystallinity of prepolymer and its changes during the polymerization affect the diffusivity and thus the polymerization rate. The diffusivity was found to be linearly proportional to the mass fraction of the amorphous phase in PET polymer.     

Structural characteristics of biodegradable thermoplastic starch/poly(ethylene–vinyl alcohol) blends

To establish relationships among the blend composition, processing history, and the resultant properties of starch-based thermoplastics, three varieties of corn starch: (1) Waxy Maize, (2) Native Corn, and (3) high-amylose Hylon VII were extrusion-blended with poly(ethylene-vinyl alcohol) (EVOH) containing 56 mol % VOH. Wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to examine the structural characteristics of the blends. All starches were destructurized upon compounding and a fine dispersion was achieved with EVOH. The Native Corn and Hylon VII blends were phase-separated and exhibited some miscibility between the polymer components as evident in EVOH melting-point depression, smaller domain sizes, lower contrast between phases in TEM, and increased resistance to moisture and enzyme-etching treatments. Starches containing amylose exhibited complexation and crystallinity in the starch fraction, although most of the crystallinity in the blends was due to the EVOH component. Waxy Maize blends were well phase-separated with larger domain sizes and underwent phase coarsening as a function of time in the melt. When subjecting the blends to capillary flow, orientation of both starch-rich and EVOH-rich domains was observed at various compositions, with the EVOH component undergoing significantly more orientation relative to starch as evident by the presence of EVOH-rich fibrils. Finally, EVOH was found to coat the surfaces of filaments produced from the blends even at rather high levels of starch (70%), which is expected to improve moisture sensitivity and slow down the initial rate of biodegradation. © 1995 John Wiley & Sons, Inc.     

Solution and solid state nuclear magnetic resonance investigation of poly(methylmethacrylate)/ poly(ethylene oxide) blends

It is well known that nuclear magnetic resonance spectroscopy (NMR) is a powerful method to characterize blends compatibility at the molecular level. In this work binary blends formed by poly(methylmethacrylate)/poly(ethylene oxide), PMMA/PEO, were investigated by different solution and solid state NMR techniques to obtain information on blends homogeneity and compatibility. It was characterized that the values of T₁^Hρ obtained by variable contact time and delayed contact time experiments, for each composition, were distinct and this fact suggests that regions with different molecular mobilities exist, as a consequence of blending interaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2955–2958, 2003     

PEALT三元共聚酯的制备及其性能研究

通过聚对苯二甲酸乙二醇酯(PET)、聚己二酸乙二醇酯(PEA)、聚L-乳酸(PLLA)3种低聚物熔融缩聚反应制备聚(对苯二甲酸乙二醇酯-己二酸乙二醇酯-乳酸)(PEALT)共聚酯。采用核磁共振仪(~1H-NMR)、差示扫描量热仪(DSC)、热重分析仪(TGA)和广角X射线衍射仪(WAXD)等测试技术对共聚酯进行了表征。     

聚(对苯二甲酸乙二醇酯-co-对苯二甲酸异山梨醇酯)预结晶及固相聚合研究

研究了不同异山梨醇(ISB)含量的聚(对苯二甲酸乙二醇酯-co-对苯二甲酸异山梨醇酯)(PEIT)共聚酯预结晶及固相聚合工艺。探讨了温度、时间与PEIT共聚酯预结晶温度、固相聚合反应速率之间的关系;利用差式扫描量热仪(DSC)分析研究PEIT共聚固相聚合前后的热性能变化情况。结果表明:随着ISB用量的增加,PEIT共聚酯结晶困难,预结晶时间增加,固相聚合反应速率减慢;随着温度升高,PEIT共聚酯固相聚合反应速率加快,但仍慢于聚对苯二甲酸乙二醇酯(PET);固相增粘后PEIT共聚酯玻璃化转变温度(Tg)与ISB含量呈线性上升关系。     

Mechanical and dynamic mechanical properties of zinc neutralized salts of poly(ethylene co-acrylic acid) and its blend with epoxidized natural rubber

Mechanical and dynamic mechanical properties of the zinc neutralized salts of poly (ethylene co-acrylic acid) (PEA) and its blends with epoxidized natural rubber (ENR) have been studied. Improvement in tensile strength, hardness (Shore-A), and a reduction in elongation at break and tension set with the increase in degree of neutralization of the blend constituents corroborate the existence of hard and rigid domains of ionic clusuters in the non-hydrocarbon and flexible backbone chain. The occurrence of a new relaxation peak due to ionic aggregates and the disappearance of the crystalline transition indicates the formation of a new ionic cluster phase in the matrix. A shift in the glass transition temperature towards higher temperature supports the existence of ionic crosslinks in the polymer matrix.     

Syntheses and characterization of poly(ethylene terephthalate) modified with p-acetoxybenzoic acid

Though the structure and properties of a copolyester of 40 mole % of polyethylene terephthalate (PET) and 60 mole % p-hydroxybenzoic acid (PHB) (PET/60PHB) and their blends have been well documented, no work has been reported in an open literature on the systematic investigation of the PET copolymers modified with broad range of p-acetoxybenzoic acid (PABA) composition as yet. In this study, several PETA-x copolyesters having various PABA compositions from 10 to 70 mole % were prepared by the melt reaction of PABA and PET without a catalyst, where x denotes the mole % of PABA. And the modified polyesters obtained were characterized by ¹H-NMR spectrophotometry, X-ray diffraction pattern, polarizing microscopy, thermal analysis, and rheometry. The anisotropic phase appeared when x is above 50 mole % of PABA, and especially for the x's of 60 and 70 mole %, the nematic liquid crystalline texture appeared clearly on the whole matrix. As the mole % of PABA increased, melting temperature, heat of fusion, crystalline temperature, degree of crystallinity, and the glass transition temperature of the modified PET were decreased, but the thermal stabilities of those copolyesters were increased. The dependence of melt viscosity on the shear rate for PETA-50 ∼ 70 followed the typical rheological behavior of liquid crystalline polymers. Finally, it was concluded that the PETA-x copolyesters having compositions of higher than 50 mole % of PABA exhibit the behavior of thermotropic liquid crystalline polymers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1707–1719, 1999     

聚酯固相缩聚等温结晶特性的研究

聚酯(PET)固相缩聚(SSP)中切片的结晶性能及其演变影响固相缩聚反应,采用差示扫描量热仪(DSC)和热台偏光显微镜研究了固相缩聚反应前后PET切片的等温结晶特性。结果表明:PET切片在DSC中的等温结晶符合Avrami 方程,等温结晶温度升高,结晶速率常数K值减小,即结晶速率降低;热台偏光显微镜中不同等温结晶温度下形成了不同的球晶形态:黑十字消光图以及环形消光图;随着PET特性粘数(平均分子质量)增大,结晶速率常数K值减小,球晶生长速率减小,Avrami指数n值增大,形成更加复杂的消光图。对于固相缩聚前PET基础切片,球晶最大结晶速率在190℃左右。     

Preparation and characterization of compatible thermoplastic dry starch/poly(lactic acid)

In the presence of glycerol and formamide, one‐step extrusion processing was used to prepare poly(lactic acid) (PLA)/thermoplastic dry starch (DTPS) blends (50/50 wt%) in a single‐screw extruder. The rheological study proved that formamide could improve the fluidity of DTPS and DTPS/PLA blends. With increasing the fluidity of DTPS, a highly dispersed and compatible DTPS/PLA could be achieved by scanning electron microscope (SEM). It was also certain that the plasticization of DTPS was improved. At the same time, Fourier transform infrared (FT‐IR) spectroscopy proved that formamide not only weakened the interaction of starch molecules, but also improved the interaction between DTPS and PLA. So that the blend could achieve more thermal stability in a compatible blend, as shown in TGA. The improvement of compatible in DTPS/PLA blends was also proved by tensile test and Dynamic mechanical thermal analysis (DMTA) in this article. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Dispersion of nanoclays with poly(ethylene terephthalate) by melt blending and solid state polymerization

Melt intercalation of clay with poly(ethylene terephthalate; PET) was investigated in terms of PET chain mobilities, natures of clay modifiers, their affinities with PET, and nanocomposite solid state polymerization (SSP). Twin screw extrusion was used to melt blend PET resins with intrinsic viscosities of 0.48, 0.63, and 0.74 dL/g with organically modified Cloisite 10A, 15A, and 30B montmorillonite clays. Clay addition caused significant molecular weight reductions in the extruded PET nanocomposites. Rates of SSP decreased and crystallization rates increased in the presence of clay particles. Cloisite 15A blends showed no basal spacing changes, whereas the basal spacings of Cloisite 10A and Cloisite 30B nanocomposites increased after melt extrusion, indicating the presence of intercalated nanostructures. After SSP these nanocomposites also exhibited new lower angle X‐ray diffraction peaks, indicating further expansion of their basal spacings. Greatest changes were seen for nanocomposites prepared from the lowest molecular weight PET and Cloisite 30B, indicating its greater affinity with PET and that shorter more mobile PET chains were better able to enter its galleries and increase basal spacing. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ultraviolet-induced crosslinking of solid poly(ethylene oxide)

Poly(ethylene oxide) (PEO) of molecular weight from 200,000 to 2,000,000 was crosslinked by exposure to ultraviolet radiation with a high-pressure 150 W mercury lamp. Photochemical crosslinking of PEO proceeds in the presence of photoinitiators such as benzophenone and acetophenone which act as a hydrogen-abstracting agent. Gel fraction yield exceeds 90%, and the number-average molecular weight between crosslinks determined by equilibrium swelling in chloroform varies from 3,000 to 100,000. The degree of crosslinking can be controlled by changing the irradiation temperature. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2299–2307, 1997     

Plasticizing effect of poly(ethylene glycol)s with different molecular weights in poly(lactic acid)/starch blends

Binary and ternary blends composed of poly(lactic acid) (PLA), starch, and poly(ethylene glycols) (PEGs) with different molecular weights (weight‐average molecular weights = 300, 2000, 4000, 6000, and 10, 000 g/mol) were prepared, and the plasticizing effect and miscibility of PEGs in poly(lactic acid)/starch (PTPS) or PLA were intensively studied. The results indicate that the PEGs were effective plasticizers for the PTPS blends. The small‐molecule plasticizers of PEG300 (i.e., the M_w of PEG was 300g/mol) and glycerol presented better plasticizing effects, whereas its migration and limited miscibility resulted in significant decreases in the water resistance and elongation at break. PEG2000, with a moderate molecular weight, was partially miscible in sample PTPS3; this led to better performance in water resistance and mechanical properties. For higher molecular weight PEG, its plasticization for both starch and PLA was depressed, and visible phase separation also occurred, especially for PTPS6. It was also found that the presence of PEG significantly decreased the glass‐transition temperature and accelerated the crystallization of the PLA matrix, depending on the PEG molecular weight and concentration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41808.     

Effect of poly(ethylene glycol) on the solid‐state polymerization of poly(ethylene terephthalate)

Poly(ethylene glycol) (PEG) and end‐capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol^?1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in T_g and similar crystallization behavior. Solid‐state polymerization (SSP) was performed on these blend samples using Sb₂O₃ as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry     

Conformation of poly(ethylene oxide) in the solid state,melt and solution measured by Raman scattering

The Raman spectrum of poly(ethylene oxide) (PEO) $\text{M}\text{?}{}_{\mathrm{w}}\text{= 3 × 10}{}^6$ and 6 × 10³ has been measured in bulk as a function of temperature and in aqueous and chloroform solution as a function of solvent concentration. The spectral features are assigned to particular isomeric configurations and the changes on melting are found to be consistent with a helix-coil transition. In both solvents the ordered nature of the polymer is largely lost at a critical concentration, approximately 50% by weight; residual ordering in dilute aqueous solution is lost and the random coil configuration attained only above the melting temperature. The wavenumber change of the 862 cm^?1 mode as a function of water concentration showed formation of a complex involving three water molecules and was consistent with a simple H-bonding model. The differences between the spectra in the two solvents are explained by this H-bonding. The results are in general agreement with n.m.r. work.