Cellulose nanocrystals reinforced poly(oxyethylene)

Nanocomposite materials were prepared from poly(oxyethylene) (POE) as the matrix and a stable aqueous suspension of cellulose nanocrystals extracted from tunicate as the reinforcing phase. After dissolving POE in water and mixing with the cellulose nanocrystals suspension, solid films were obtained by casting and evaporating the preparations. Resulting films were characterized using scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis. Favorable interactions between cellulose and POE were evidenced and assumed to be partially responsible for a decrease of the crystallinity of the matrix. A thermal stabilization of the nanocomposites for temperatures higher than the melting temperature of POE was reported and ascribed to the formation of a rigid cellulosic network within the matrix assumed to be governed by a percolation effect. The formation of this percolating network was not altered by the matrix crystallization process and filler/POE interactions.     

Experimental verification on upper critical solution temperature (UCST) behavior in blend of poly(2,6-dimethyl p-phenylene oxide) with poly(4-methyl styrene)

Rare upper critical solution temperature (UCST) behavior was found and experimentally demonstrated in the blend comprising poly(2,6-dimethyl p-phenylene oxide) with poly(4-methyl styrene) (PPO/P4MS). Complexity of phase behavior in the PPO/P4MS system has caused puzzling analyses in the past years. This study re-investigated and clarified past mis-interpretations related to this interesting blend system. This study concluded that the PPO/P4MS blend is an immiscible system at ambient, which, however, turns into a miscible phase with UCST behavior at higher temperatures. With the finding of UCST in the PPO/P4MS blend, a critical contribution of this work was to resolve the conflicting arguments that have gone on for a long time in determination and interpretation of the thermodynamic phase behavior of PPO/P4MS. Phase behavior with UCST in the PPO/P4MS blend system and its interpretation were supported with clear experimental evidence.     

Type-A dipole moment and segmental dynamics of poly(styrene oxide)

We report the dielectric properties of poly(styrene oxide)s (PSO) in bulk and concentrated solution states. Since the structure of PSO is asymmetric along the backbone, the repeat unit of PSO is expected to possess the non-zero component of the dipole moment p_A parallel to the chain contour as well as the perpendicular component p_B. The former and latter cause the dielectric normal mode and segmental mode relaxations, respectively. Contrary to the above mentioned expectation the temperature dependence of ε″ exhibits only the primary (α) relaxation and weak secondary relaxation (β) in the glassy state. No loss peak due to the normal mode relaxation was observed in the frequency region expected from the viscoelastic terminal relaxation in bulk and toluene solutions. The dielectric behaviours of the α relaxation in the bulk state were analyzed in detail and the parameters of the Vogel-Fulcher and the Havriliak-Negami equations were determined. The Kirkwood correlation factor was determined to be 0.36. The ¹³C NMR spectra indicate that the present PSO samples contain about 2% head-to-head linkages. This cannot be the origin of the disappearance of the normal mode. We conclude that p_A of PSO is too small to be detected. The p_A calculated with molecular orbital methods supports this conclusion.     

Synthesis, characterization and pyrolysis of poly(styrene/divinylbenzene) derivatives

A series of polyfstyrene/divinylbenzene) derivatives were prepared and characterized by solid-state ¹³C FT-NMR, FT-IR, elemental analysis, SEM and TGA. The resins were then subjected to pyrolysis in order to determine which derivatives resulted in high yields of carbonaceous material while retaining a spherical shape.     

Morphology and properties tuning of PLA/cellulose nanocrystals bio-nanocomposites by means of reactive functionalization and blending with PVAc

A novel method for the preparation of PLA bio-nanocomposites containing cellulose nanocrystals (CNCs) is reported. In order to enhance interfacial adhesion and dispersion of nanocrystals into PLA matrix, functionalization of PLA and CNCs by radical grafting of glycidyl methacrylate (GMA) and pre-dispersion of CNCs in poly (vinyl acetate) (PVAc) emulsion were applied. Morphologies, thermal and mechanical properties of nanocomposites for CNCs content of 1–6 wt.% were examined. Addition of functionalized components (PLA-GMA, CNC-GMA) and/or PVAc dispersed CNCs both improved the phase distribution of nanofiller and tensile properties, compared to the binary PLA/CNC nanocomposites. Thermal analyses demonstrated that glass transition, melting temperature and crystallinity of PLA were affected by the PVAc amount. Nanocomposites with PVAc dispersed CNCs exhibited higher thermal resistance than other composites. The filler effectiveness (CFE) was evaluated for all samples on the basis of storage modulus values: CNC-GMA and PVAc dispersed CNCs (3 wt. %) resulted the most effective fillers.     

Polymer micelle-like aggregates of novel amphiphilic biodegradable poly(asparagine) grafted with poly(caprolactone)

Novel amphiphilic graft copolymers composed of poly(asparagine) (PAsn) as the hydrophilic backbone and poly(caprolactone) (PCL) as the hydrophobic segment were successfully synthesized by grafting PCL-HMDs to poly(succinimde). After tosylating PCL-diol with p-toluenesulfonylchloride (TsCl), tosylated poly(caprolactone) (PCL-OTs) was then reacted with hexamethylenediamine (HMD). The reaction of the amine terminated PCL with poly(succinimide) (PSI) and the following aminolysis resulted in poly(aspargine)-graft-poly(caprolactone) (PAsn-g-PCL). The degree of substitution (DS) and grafting reaction was confirmed by ¹³C NMR, FT-IR spectroscopy and elemental analysis. X-ray diffraction and DSC thermogram showed that the crystalline domain originated from PCL became apparent with an increase of DS. The amphiphilic comb-type graft polymer formed self-aggregates in aqueous solution when precipitated and dialysed against distilled water. Strong hydrophobic interaction of associated PCL grafts facilitated primary aggregate formation with DS, significantly reducing critical aggregation concentration and secondary aggregates also appeared in DLS measurements. Self-aggregates showed a bimodal size distribution originated from the self-aggregation and kinetically controlled particle aggregation, although the smaller primary aggregates was predominant. Spherical and dispersed aggregates of about 20 nm in diameter were observed by a transmission electron microscope.     

Synthesis and characterization of poly(pyridinium salt)s with organic counterion exhibiting both lyotropic liquid-crystalline and light-emitting properties

Two poly(pyridinium salt)s containing a bulky organic counterion such as 2-naphthalenesulfonate were synthesized by the ring-transmutation polymerization reaction of bis(pyrylium 2-naphthalenesulfonate) with the corresponding aromatic diamines on heating in dimethyl sulfoxide (DMSO) at 145-150 °C for 24 h, and characterized for their lyotropic liquid crystalline as well as fluorescence properties in both polar protic and aprotic solvents such as methanol and DMSO. Their polyelectrolyte behavior in DMSO was also determined by solution viscosity measurements.     

Synthesis and characterization of poly(pyridinium salt)s with anthracene moieties exhibiting both lyotropic liquid-crystalline and UV light-emitting properties

Two poly(pyridinium salt)s with anthracene moieties in the main chain as well as tosylate and triflimide as counterions were prepared by either the ring-transmutation polymerization of phenylated bis(pyrylium tosylate) salt with 2,6-diaminoanthracene in dimethyl sulfoxide or the metathesis reaction of the corresponding tosylate polymer with lithium triflimide in acetonitrile. They were characterized for their lyotropic liquid-crystalline and UV light-emitting properties, with various experimental techniques. These ionic, conjugated anthracene polymers are the recent addition to the class of UV light-emitting polymers, since they emit UV light both in solution and in the solid state.     

Surface morphology and Flory-Huggins interaction strength in UCST blend system comprising poly(4-methyl styrene) and isotactic polystyrene

The surface morphology and polymer-polymer interaction parameter (χ₁₂) of UCST blend systems comprising isotactic polystyrene and poly(4-methyl styrene) (P4MS) were investigated using atomic-force microscopy (AFM) and differential scanning calorimetry (DSC). From the measured glass transition temperature and the specific heat increments (ΔC_p) at T_g, it was found that the P4MS dissolved more easily in the iPS rich-phase than did the iPS in the P4MS rich-phase. AFM result also supported that the compatibility increased more in the regions of P4MS-rich compositions than in the regions of PS-rich compositions of the PS/P4MS blends. From the measured T_g’s and apparent weight fractions of iPS and P4MS dissolved in each phase, the values of the Flory-Huggins interaction parameter (χ₁₂) were determined to be 0.0163-0.0232 depending on the composition. These results indicate that the χ₁₂ is quite dependend on the apparent volume fraction of the polymers dissolved in each phase. The values of χ₁₂ calculated from this work (method based on T_g’s of phases) were lower than those estimated using an earlier method based on the UCST or clarity temperatures. All values of χ₁₂ are greater than the values of interaction parameter at the critical point (χ₁₂)_c. This fact indicates that the iPS/P4MS blend are immiscible for all blend compositions. The surface of the phase-separated blend system was mostly covered with the P4MS rich-phase owing to its lower surface free energy in comparison with that of the neat iPS. The mechanism of surface phase separation for the P4MS blends with aPS or iPS is governed by two factors: (1) difference in the solubility of the two polymers in the solvent and (2) surface free energy.     

Nanoscale artifacts in RuO4-stained poly(styrene)

This research studies the effects of RuO₄ exposure on various samples of poly(styrene) (PS). Transmission electron energy-loss spectroscopy (EELS) shows a decrease in the 7 eV π-π∗ transition characteristic of aromatic rings in PS indicating that RuO₄ covalently alters aromatic character. Imaging and selected-area electron diffraction show that a layer of RuO₂ solid forms on the surface of bulk PS specimens exposed to RuO₄. High-resolution TEM imaging (HREM) shows that RuO₂ nanocrystals consistently condense on specimen surfaces, independent of the chemical nature of the specimen below. These nanocrystals modulate contrast at length scales on the order of 2-5 nm in TEM images and limit resolution at nanometer length scales.     

Nanocomposites of poly(propylene carbonate) reinforced with cellulose nanocrystals via sol‐gel process

Cellulose nanocrystals (CNCs) organogels were first produced from aqueous dispersion through solvent exchange of CNCs to acetone via a simple sol‐gel process. After mixing the organogels with poly(propylene carbonate) (PPC) in dimethylformamide followed by solution casting, green nanocomposites were obtained with CNCs well dispersed in PPC polymer matrix which was confirmed by scanning electron microscopy observations. Differential scanning calorimeter analysis revealed that glass transition temperature of the nanocomposites was slightly increased from 34.0 to 37.4°C. Tensile tests indicated that both yield strength and Young's modulus of CNCs/PPC nanocomposites were doubled by adding 10 wt % CNCs. However, poor thermal stability of PPC occurred after incorporating with CNCs due to the thermo‐sensitive sulfate groups located on the surface of CNCs. Furthermore, PPC became more hydrophilic because of the inclusion of CNCs according to the water contact angle measurement. The enhanced mechanical and hydrophilic properties, coupled with the inherent superior biocompatibility and degradability, offered CNCs/PPC composites potential application in biomedical fields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40832.     

Enhanced oxygen barrier property of poly(ethylene oxide) films crystallite-oriented by adding cellulose single nanofibers

In this study, we investigated the influence of cellulose single nanofibers (CSNFs) added to poly(ethylene oxide) (PEO) on the microstructure and property to create high gas barrier films. The CSNF/PEO nanocomposite films were prepared by solvent casting. The PEO crystallite orientation was measured using wide-angle X-ray diffraction of the SPring-8 synchrotron radiation facility. The degree of crystallite orientation was evaluated from the reflections of the PEO (1 2 0) lattice planes to investigate quantitatively the effect of different amounts of the additive CSNFs. The crystallite orientation of PEO increased with the addition of the CSNF. Furthermore, the oxygen barrier property for each nanocomposite film was found to be higher than that of the pure PEO film. The 5 wt% addition of CSNFs was mostly effective in enhancing the PEO crystallite orientation and oxygen barrier.     

Compatibilization of poly(methyl methacrylate) and cellulose nanocrystals through co-continuous phase to enhance the thermomechanical properties

The present study focuses on enhancing the thermomechanical properties of poly(methyl methacrylate) (PMMA), a transparent and biocompatible polymer known for its high strength but limited toughness. The approach involves the development of PMMA/cellulose nanocrystals (CNCs) composites. To improve the interfacial compatibility between PMMA and CNCs, a two-step process is employed. Initially, the CNCs undergo oxidation using sodium periodate, followed by the introduction of amino groups through reductive amination. The aminated CNCs are then covalently bonded to PMMA via an amidation reaction using the “grafting onto” approach. Subsequently, the grafted CNCs are incorporated into the PMMA matrix using the solvent casting method. The resulting composites are extruded into filaments. Elemental composition analysis confirms CNC modification, revealing the presence of 1.6% nitrogen. The modified CNCs exhibit a higher degradation temperature than unmodified CNCs, showing a 50°C increase. The composites' dynamic mechanical analysis (DMA) reveals a 20% improvement in storage modulus (E′) upon incorporating 1.5% of the grafted CNCs into the PMMA matrix. This enhancement is attributed to the formation of co-continuous phases in the composite structure.     

Intermolecular interaction in aqueous solution of binary blends of poly(acrylamide) and poly(ethylene glycol)

The interaction between poly(acrylamide) (PAM) and poly(ethylene glycol) (PEG) in their solid mixture was studied by Fourier transform infrared spectroscopy (FTIR); and their interaction in aqueous solution was investigated by nuclear magnetic resonance spectroscopy (NMR). For the solid PAM/PEG mixtures, an induced shift of the >C?O and >N? H in amide group was found by FTIR. These results could demonstrate the formation of intermolecular hydrogen bonding between the amide group of PAM and the ether group of PEG. In the aqueous PAM/PEG solution system, the PAM and PEG associating with each other in water, i.e., the amide group of PAM interacting with the ether group of PEG through hydrogen bonding was also found by ¹H NMR. Furthermore, the effects of different molecular weight of PAM on the strength of hydrogen bonding between PAM and PEG in water were investigated systemically. It was found that the hydrogen bonding interaction between PAM and PEG in water did not increase with the enlargement of the PAM molecular weight as expected. This finding together with the viscosity reduction of aqueous PAM/PEG solution with the PAM molecular weight increasing strongly indicated that PAM molecular chain, especially having high molecular weights preferred to form spherical clews in aqueous PEG solution. Therefore, fewer amide groups in PAM could interact with the ether groups in PEG. Based on these results, a mechanism sketch of the interaction between PAM and PEG in relatively concentrated aqueous solution was proposed. The fact that the phase separation of aqueous PAM/PEG solution occurs while raising the temperature indicates that this kind of hydrogen bonding between PAM and PEG in water is weak and could be broken by controlling the temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

高交联大孔St—DVB共聚物的合成及吸附性能

研究了高交联大孔Ｓｔ－ＤＶＢ共聚物的吸附特性与其所使用的混合致孔剂的种类,第三组分及其交联度的关系,结果表明：当二甲苯：煤油：第三组分＝９：１０：１,第三组分为环己酮,交联度为４０．％,树脂的吸附性能最佳,其吸附容量为５０．０ｍｇ酚／ｍｌ树脂。     

Predicted miscibility of polystyrene and poly(α-methyl styrene) and comparison with experiment

The free energy of mixing of polystyrene with poly(α-methyl styrene) has been calculated using the Flory-Huggins expression and the more recent Flory theory which takes account of free volume effects. The double tangents to the free energy-composition curves were used to define phase separation points and hence the expected phase diagram for the system. Both approaches reproduce the observed behaviour reasonably well but in the latter case this is true only if a semi-empirical entropy parameter is included. The interaction of the polymers with the solvents used to prepare the blends is discussed.     

Embedding poly(styrene sulfonic acid) into PVDF matrix—a new type of proton electrolyte membrane

Hydrophilic polymer segments, consisting of styrene sulfonic acid (SSA) units, were uniformly embedded into hydrophobic poly(vinylidene fluoride) (PVDF) matrix through the mediation of poly(methyl methacrylate) (PMMA) segments, with which SSA segments form a copolymer. Discrete domains (∼100 nm) assembled by the SSA segments have been identified throughout the matrix of the membrane, which was prepared through blending of the copolymer P(MMA-SSA) and the PVDF. The thermal stability of the SSA was largely boosted in such hydrophobic environment. This unique matrix structure offers proton conductivity of as high as 10⁻³ S/cm at a low SSA equivalent (0.6 mmol -SO₃H/g of membrane), which is accompanied with a low level of water uptake (26%) at ambient temperature. Using this type of polymer membrane as electrolyte, the electrochemical cell possesses obvious capacitive resistance when the membrane is in the anhydride form according to the impedance analysis. However, the capacitive character vanishes when the membrane is hydrated; this response is attributed to the existence of highly dispersed SSA domains in the membrane. This work also analyzes the impedance spectra of the membranes at different hydrated states or with different SSA contents by using an equivalent electrical circuit.     

Modification of poly(styrene) by reactive blending with nitrificated rubber

A possible way to obtain modified poly(styrene) (PS) with a new complex of properties: 2–3 times higher impact resistance in a combination with significantly increased tensile strength and bending strength, 6–8 times higher flowability and strongly increased adhesion is described here. It is established that the modified PS new properties complex is a result from an elastification, nitrification, structure modification, and “critical” phenomena in the two component system studied. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 638–645, 2001     

Development and characterization of bionanocomposites based on poly(3‐hydroxybutyrate) and cellulose nanocrystals for packaging applications

Poly(3‐hydroxybutyrate) (PHB)‐based bionanocomposites were prepared using various percentages of cellulose nanocrystals (CNCs) by a solution casting method. CNCs were prepared from microcrystalline cellulose using sulfuric acid hydrolysis. The influence of CNCs on PHB properties was evaluated using differential scanning calorimetry, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetry and tensile testing. Vapor permeation and light transmission of the materials were also measured. Differential scanning calorimetric tests demonstrated that CNCs were effective PHB nucleation agents. Tensile strength and Young's modulus of PHB increased with increasing CNC concentration. Moreover, the PHB/CNC bionanocomposites exhibited reduced water vapor permeation compared to neat PHB and had better UV barrier properties than commodity polymers such as polypropylene. It was found that nanocomposites with 6 wt% of CNCs had the optimum balance among thermal, mechanical and barrier properties. © 2016 Society of Chemical Industry     

Intermolecular interactions and crystallization behaviors of biodegradable polymer blends between poly (3-hydroxybutyrate) and cellulose acetate butyrate studied by DSC, FT-IR, and WAXD

Relationships between composition- and temperature-dependent intermolecular interactions and cold crystallization behaviors of poly(3-hydroxybutyrate) (PHB)/ cellulose acetate butyrate (CAB) blends have been investigated mainly by infrared (IR) spectroscopy, together with differential scanning calorimetry, and wide-angle X-ray diffraction (WAXD). Weak intermolecular hydrogen bondings between OH groups in CAB and CO groups in amorphous part of PHB define as inter were detected in OH stretching bands of the blends. These interactions occur in the blends with high CAB content (w_CAB) and highly depend on temperature. For all the blends having 0.2 ≤ w_CAB ≤ 0.7, when temperature is raised (e.g., above 90 °C for the blend with w_CAB = 0.5) the cold crystallization of PHB was discerned, as evidenced by an increase of the absorbance of the band due to CO stretching in the crystal field. The crystallization was found to involve the dissociation of inter and transformation of inter into intramolecular hydrogen bondings within PHB and within CAB as summarized in Table 2 in this text, which promotes the crystallization and enhances stabilization of the crystals. Consequently, the crystallization of the PHB is influenced by exchanges of the hydrogen bondings as described above with raising temperatures. X-ray diffraction from PHB crystals in the blends show a remarkable decrease of crystallinity with w_CAB and eventually disappear when w_CAB ≥ 0.8.