Oligomer Blends Research Articles

Non-intuitive Trends in Flory–Huggins Interaction Parameters in Polyether-Based Polymers

Recently, a variety of “click” or other additive chemistries have been introduced to functionalize polymers after polymerization to target specific applications, for example, membranes, catalysis, or drug delivery systems. It is generally assumed that the inclusion of these “click” linking groups has minimal impact on the thermodynamics of the polymer as a whole. In this study, we demonstrate that the introduction of these click-derived units has a profound impact on the Flory–Huggins parameter of polyether derivatives. Using random phase approximation fits for small-angle X-ray scattering data from block copolymer pairs to estimate the Flory–Huggins interaction parameter (χ), we determined that poly(ethylene oxide) (PEO) and poly(allyl glycidyl ether) (PAGE), which differ only by the inclusion of an allyl sidechain, have a χ of 0.030 (at T = 34 °C). While PEO is miscible with poly(lactide) (PLA) at nearly all temperatures, the PLA/PAGE χ determined experimentally is 0.015 (at T = 30 °C). Atomistic molecular dynamics simulations of PEO/PAGE oligomer blends show that upon blending, PEO chains contract and move closer together, while PAGE chains stretch and spread apart, indicating an enthalpic contribution to the χ parameter due to changes in polymer coordination resulting from the conformational asymmetry of PAGE and PEO. These studies demonstrate the large impact that functionalization and side-chain units have on the χ parameter of polymer pairs.

Fullerene‐Free Polymer Solar Cells with Open‐Circuit Voltage above 1.2 V: Tuning Phase Separation Behavior with Oligomer to Replace Polymer Acceptor

This study has proposed to use a well‐defined oligomer F4TBT4 to replace its analogue polymer as electron acceptor toward tuning the phase separation behavior and enhancing the photovoltaic performance of all‐polymer solar cells. It has been disclosed that the oligomer acceptor favors to construct pure and large‐scale phase separation in the polymer:oligomer blend film in contrast to the polymer:polymer blend film. This gets benefit from the well‐defined structure and short rigid conformation of the oligomer that endows it aggregation capability and avoids possible entanglement with the polymer donor chains. The charge recombination is to some extent suppressed and charge extraction is also improved. Finally, the P3HT:F4TBT4 solar cells not only output a high VOC above 1.2 V, but also achieve a power conversion efficiency of 4.12%, which is two times higher than the P3HT:PFTBT solar cells and is comparable to the P3HT:PCBM solar cells. The strategy of constructing optimum phase separation with oligomer to replace polymer opens up new prospect for the further improvement of the all‐polymer solar cells.

Effect of side chain length on the morphology of blends of 2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐b]thiophene oligomers and fullerene derivatives

ABSTRACTUsing molecular dynamics simulations we study blends of oligomers of 2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐b]thiophene, BTTT, and fullerene derivative based acceptors to understand the role of oligomer length and alkyl side chain (SC) length on the morphology of their blends. We use a validated coarse‐grained model of BTTT and fullerene derivatives presented in recent work along with direct comparison of morphology between simulations and experiments. In this article, we predict computationally that short alkyl SCs (6 alkyl groups) decrease the propensity of fullerene derivative acceptors to intercalate between SCs on the BTTT backbone compared to longer alkyl SCs (9 or 12 alkyl groups), and as a result increase acceptor aggregation. The decreasing acceptor intercalation and increasing acceptor aggregation do not significantly impact the positional or orientational order of the BTTT backbones. However, the BTTT oligomer backbones order better with increasing SC length in both neat systems and in blends, with the blends exhibiting higher positional order than neat systems. While these qualitative trends are similar both in 2mer blends and 4mer blends, we see a larger extent of acceptor intercalation and as a result, smaller acceptor cluster sizes in the 4mer blends. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 89–97

Features of the melt flow of polyethylene and boron oxide oligomer blends

The features of melt flow of LDPE and boron oxide oligomer blends during extrusion mixing are investigated. It is established that the extruder-wall pressure and the torque of the screw decrease monotonically with an increase in the boron oxide oligomer content up to 25 vol %. Exceeding this concentration threshold leads to a several-fold stepwise fall in of the mentioned characteristics. This result is explained within the concepts about spontaneous restructuring of the blend accompanied by an increase of the specific surface of phases and by slipping at the interface of the blend components that is caused by the planar structure of the boron oxide oligomer molecules.

Polyurethane adhesive composition cured at room temperature

The influence of polyfunctional hydroxyl-containing oligomer on the rheological, physicomechanical, and adhesive properties of polyurethane composite based on multicomponent oligomer blend and polyisocyanate is investigated. The kinetics of curing is investigated by the viscometric method, and the composition lifetime is determined. It is shown that the polyurethanes under investigation can be used as fast-curing adhesive composites of cold curing operating in a temperature interval of up to +90°C.

Anti-biofouling 3D porous systems: the blend effect of oxazoline-based oligomers on chitosan scaffolds

The production, characterization and anti-biofouling activity of 3D porous scaffolds combining different blends of chitosan and oxazoline-based antimicrobial oligomers is reported. The incorporation of ammonium quaternized oligo(2-oxazoline)s into the composition of the scaffold enhances the stability of the chitosan scaffold under physiological conditions as well as its ability to repel protein adsorption. The blended scaffolds showed mean pore sizes in the range of 18–32 μm, a good pore interconnectivity and high porosity, as well as a large surface area, ultimate key features for anti-biofouling applications. Bovine serum albumin (BSA) adhesion profiles showed that the composition of the scaffolds plays a critical role in the chitosan–oligooxazoline system. Oligobisoxazoline-enriched scaffolds (20% w/w, CB8020) decreased protein adsorption (BSA) by up to 70%. Moreover, 1 mg of CB8020 was able to kill 99.9% of Escherichia coli cells upon contact, demonstrating its potential as promising material for production of tailored non-fouling 3D structures to be used in the construction of novel devices with applications in the biomedical field and water treatment processes.

Disperse Systems Based on the Structure and Properties of Oligomer Blends

This article demonstrates the potential for both homogeneous and heterogeneous structures to form in oligomer blends. The nature of the dependence of viscosity on the composition of the heterophase blend has been found to be governed by the phenomenon of wetting of the surface of the disperse phase dispersion medium. Selectivity offiller distribution in oligomer blends is shown. Also demonstrates the potential for filler formation during the actual composite matrix curing process.

Fracture and Deformation of Extended-Chain Crystals in Poly(ethylene Terephthalate)/Bisphenol-A Polycarbonate Blends Crystallized at High Pressure

With a combination of three-dimensional crystal ordering and long-chain molecular orientational ordering, the extended-chain crystals of polymers are ideal system for the studies on low-dimensional physics, and have potential applications as functional components. In this study, poly (ethylene terephthalate) / bisphenol-A polycarbonate (PET/BAPC) blend samples were prepared with solid phase forming technique under high pressure, and extended-chain single crystals with large c-axis thickness were formed within a relative short time. The fracture and deformation behaviors of the grownup crystals were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Morphological observation showed that most of the extended-chain crystals were endowed with perfect appearance after the sample fracture. However, there were still a few crystals fractured apart, along or perpendicularly to their c-axis direction, or with cohesive fracture surfaces. Fractured spherulites with extended-chain lamellae as substructures were also disclosed in extended-chain crystals with AFM. Furthermore, the parallel lamellae deformed and changed their striation direction during the crystal growth, as was observed on a kind of extended-chain crystals grown in a PET oligomer and BAPC blend (PETO/BAPC). This study may be instructive to the improvement of the separation technique of such single crystals, so as to hasten their real applications.

Solvent Annealing Induced Perpendicular Orientation of Cylindrical Microdomains in Polystyrene-b-poly(4-hydroxyl styrene)/PEG Oligomer Blend Thin Film Made by Spin-coating from Selective Solvent

The microphase separated structure of PS-b-PHS/PEG blend thin film with thickness of 500 ~ 600 nm was investigated by grazing incidence small angle X-ray scattering. The thin film was obtained by two different solutions; one was THF which was common good solvent for all components of polymers used here. The other is toluene which was selective solvent for PS and poor-solvent for PHS and PEG. The equilibrium morphology of the block copolymer and blend sample was hexagonally packed cylinder in the bulk and thin film. The structure in the thin film obtained by spin cast from toluene solution was non-equilibrium. After THF vopar annealing of the thin film (cast from toluene), the highly ordered and perpendicular oriented cylindrical structure was obtained. Perpendicular orientation was failure when the thin film sample made by spin cast from THF solution and subsequent THF vapor annealing. The perpendicular nano-holes were fabricated after removing PEG oligomer by washing with water.

Dielectric behaviour and relaxation processes of montmorillonite clay nano‐platelet colloidal suspensions in poly(vinyl pyrrolidone)–ethylene glycol oligomer blends

AbstractBACKGROUND: Intercalated and exfoliated montmorillonite (MMT) clay structures in polymer matrices improve the thermal, mechanical, electrical and pharmaceutical properties of organic–inorganic materials. Poly(vinyl pyrrolidone) (PVP)–ethylene glycol oligomer (EGO) blends are biocompatible and non‐toxic materials. The dielectric characterization of MMT clay nano‐platelet colloidal suspensions in PVP–EGO blends is important in understanding the ionic conduction behaviour in many complex phenomena occurring in biological systems, and in selective membranes and their use in controlled drug release systems and in liquid electrolytes.RESULTS: An investigation using dielectric spectroscopy in the 20 Hz to 1 MHz frequency range of MMT clay nano‐platelet colloidal suspensions in PVP–EGO blends confirmed that the PVP segmental motion, ionic conduction relaxation time, electric double layer relaxation time and direct current electrical conductivity are significantly influenced by the clay concentration and EGO chain length. In these materials, ionic motion and PVP segmental dynamics are strongly coupled. Intercalation of EGO structures in clay galleries and exfoliation of clay platelets by adsorption of PVP–EGO structures on clay surfaces are governed by hydrogen bonding interactions between the carbonyl groups of PVP monomer units, the hydroxyl groups of EGOs and the hydroxylated aluminate surfaces of the MMT clay.CONCLUSION: The dielectric behaviour of intercalated and exfoliated structures of MMT clay nano‐platelet colloidal suspensions in PVP–EGO blends provides a convenient way to obtain liquid organic‐inorganic polymeric nanocomposite electrolytes with tailored ionic conduction properties. Copyright © 2009 Society of Chemical Industry

Mesoscopic order and the dimensionality of long-range resonance energy transfer in supramolecular semiconductors

We present time-resolved photoluminescence measurements on two series of oligo-p-phenylenevinylene materials that self-assemble into supramolecular nanostructures with thermotropic reversibility in dodecane. One set of derivatives form chiral helical stacks, while the second set form less organized "frustrated" stacks. Here we study the effects of supramolecular organization on the resonance energy transfer rates. We measure these rates in nanoassemblies formed with mixed blends of oligomers and compare them with the rates predicted by Forster theory. Our results and analysis show that control of supramolecular order in the nanometer length scale has a dominant effect on the efficiency and dimensionality of resonance energy transfer.

Synergistic effect of polymer and oligomer blends for solution-processable organic thin-film transistors

The thin-film morphologies and thin-film transistor (TFT) characteristics of a series of binary blends of poly(9,9′-dioctylfluorene- alt-bithiophene) (F8T2) and α, ω-dihexylquarterthiophene (DH4T) are reported. The blends of F8T2 and DH4T exhibit good solubility and produce TFT devices with better performances than F8T2 and DH4T devices. The 50% DH4T blend device was found to have a hole mobility of 0.011 cm 2 V −1 s −1, which is four times higher than the mobility of the F8T2 device, with a high-on/off ratio of about 10 5 and a low-off current of 17 pA. The polymer and oligomer domains are phase-separated with large domain size and arranged in characteristic molecular alignments. It was found that carrier transport in the blend systems is mainly controlled by the polymer component, and that the nature of the blended oligomer affects the OTFT performance of the blends.

Oligomer blends: Rheology, structure, and properties

The specifics of the phase structure, rheological properties, and mechanical characteristics of cured and liquid blends of reactive oligomers are discussed, as well as filled compositions in the form of emulsions on their basis. One of the main factors that determine the properties of these blends is their phase composition and the colloid-chemical structure. In the filled emulsions, an uneven distribution of filler between the phases is possible. If the emulsion structure of the two-phase blends of reactive oligomers is fixed during their curing, the blends may exhibit quite surprising properties.

Thermal properties and combustion behaviors of UV‐cured phosphate triacrylate/star poly(urethane acrylate) oligomer blends

AbstractA series of UV‐curable intumescent flame retardant resins was obtained by blending phosphate triacrylate (TAEP) in certain ratios with star poly(urethane acrylate) (SPUA) oligomer. The flammability of the cured films was characterized by limited oxygen index (LOI), UL 94, and the cone calorimeter. The results showed that the cured TAEP/SPUA samples greatly expanded while burning. A distinct synergistic effect was found between TAEP and SPUA. TAEP2 sample showed the highest LOI value (41) among all resins. The cone calorimeter results showed that the peak heat release rates and carbon monoxide yield decreased to the approximate level. The degradation was monitored by thermogravimetric analysis and real‐time Fourier transform infrared spectroscopy. A degradation mechanism is suggested in which the phosphate group in TAEP first degraded to form poly(phosphoric acid)s, which further catalyzed the degradation of the material to form char with emission of carbon dioxide and nitrogen volatiles from SPUA, leading to the formation of expanding char. The morphologic structures of crusts of the formed chars were observed by scanning electron microscopy, demonstrating the synergistic effect between TAEP and SPUA. Copyright © 2008 John Wiley & Sons, Ltd.

The glass transition in athermal poly(α‐methyl styrene)/oligomer blends

AbstractThe glass transition behavior in athermal blends of poly(α‐methyl styrene) (PaMS) and its hexamer is investigated using differential scanning calorimetry (DSC). The results, along with previous data on similar blends of PaMS/pentamer, are analyzed in the context of the Lodge–McLeish self‐concentration model. A methodology is described to partition the calorimetric transition to obtain effective Tgs for each component of the blend. The dependences of these effective Tgs on overall blend composition are described by the Lodge–McLeish model, although the self‐concentration effect is less than expected based on the Kuhn length. The length scales of the cooperatively rearranging regions for the two components in the blends are also calculated adapting Donth's fluctuation model to the partitioned DSC transitions and are found to be similar for the two components and show a slight decrease at intermediate concentrations. The kinetics associated with the glass temperature, Tg, is examined by studying the cooling rate dependence of Tg for the pure components and the blends, as well as by examining the enthalpy overshoots in the heating DSC scans. It is observed that the cooling rate dependence of Tg in PaMS/hexamer blends at intermediate concentrations is similar to that of the hexamer, indicating that the kinetics of the glass transition for blends is dominated by the high mobility oligomeric component. Moreover, compared to the pure materials, the PaMS/hexamer blends exhibit a considerably depressed enthalpy overshoot, presumably resulting from their broader relaxation time distribution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 418–430, 2008

Dynamic interplay between phase separation and crystallization in a poly(ɛ-caprolactone)/poly(ethylene glycol) oligomer blend

We have investigated the crystallization effect on the phase separation of a poly(ɛ-caprolactone) and poly(ethylene glycol) oligomer (PCL/PEGo) blending system using simultaneous small-angle light scattering and differential scanning calorimetry (SALS/DSC) as well as simultaneous small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and DSC (SAXS/WAXS/DSC). When the PCL/PEGo system, of a weight ratio of 7/3, is quenched from a melt state (160 °C) to temperatures below the spinodal point and the melting temperature of PCL (63 °C), the structural evolution observed exhibits characteristics of (I) early stage of spinodal decomposition (SD), (II) transient pinning, (III) crystallization-induced depinning, and (IV) diffusion-limited crystallization. The time-dependent scattering data of SALS, SAXS and WAXS, covering a wide range of length scale, clearly show that the crystallization of PCL intervenes significantly in the ongoing viscoelastic phase separation of the system, only after the early stage of SD. The effect of preordering before crystallization revives the structural evolution pinned by the viscoelastic phase separation. The growth of SAXS intensity during the preordering period conforms to the Cahn–Hilliard theory. In the later stage of the phase separation, the PCL-rich matrix, of spherulite crystalline domains developed due to the faster crystallization kinetics, traps the isolated PEGo-rich domains of a slower viscoelastic separation.

Sustained delivery of growth factors from methylidene malonate 2.1.2-based polymers

The incorporation of growth factors into new methylidene malonate 2.1.2-based biocompatible polymeric blends of oligomers and polymers to improve their stability and controlled release was investigated. Five growth factors were used in this study: FGF2, PDGF, TGF- β, NGF and GM-CSF. Formulation in poly(methylidene malonate 2.1.2) blends was achieved by a four-step optimized process, using different oligomers/polymers ratios. Once dried, formulations could be subsequently stored at 4 or 20 °C or immediately subjected to degradation in conditioned cell culture medium. Toxicity of blends and their degradation products were evaluated in several cell lines with MTT. Bioactivity and biospecificity of the formulated growth factors were investigated using MTT and immunohistochemical staining. Combined ELISA and crystal violet colorimetric assays were performed to analyze growth factors release. Limited toxicities were observed for unloaded poly(methylidene malonate 2.1.2) blends. Once optimized, growth factors formulations did not reveal lower bioactivities or loss of biospecificity. Moreover, a sustained release over a 21-day period with more than 90% of preserved bioactivity was reached. To conclude, dual growth factor delivery was made possible by the mean of poly(methylidene malonate 2.1.2) blends. These studies demonstrate the ability of methylidene malonate 2.1.2-based polymeric blends for the delivery of growth factors.

Thermomechanical film properties and aging of blends of poly(lactic acid) and malonate oligomers

AbstractMalonate oligomers were synthesized as plasticizers for poly(lactic acid) (PLA). Esterification reactions were performed between diethyl bishydroxymethyl malonate (DBM) and either adipoyl dichloride or succinyl dichloride. Two molar masses were obtained within each series. Blending was carried out with PLA and the four oligomers as well as the monomeric unit from the syntheses (DBM). Dynamic mechanical analysis and differential scanning calorimetry were used to investigate the viscoelastic mechanical and thermal film properties of the blends. All the investigated plasticizers reduced the glass‐transition temperature of PLA, and the plasticization effect was better for the plasticizers of low molar mass. However, the amorphous domains of PLA became saturated with plasticizer at a certain concentration, and phase separation occurred. A higher molar mass of the plasticizer caused this saturation to occur at lower plasticizer concentrations. Subsequently, the aging of the blends at the ambient temperature for 4 months induced phase separation in the blends containing DBM, whereas those with an oligomeric plasticizer were stable and remained compatible with PLA within the aging period. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2140–2149, 2004

Evaluation of anhydride oligomers within polymer microsphere blends and their impact on bioadhesion and drug delivery in vitro

The effect of the addition of small molecular weight anhydride oligomers to polymer microspheres was evaluated and increased bioadhesion of the composite was demonstrated. Blends of low molecular weight anhydride oligomers with thermoplastic poly(fumaric-co-sebacic anhydride) [p(FASA)] and polycaprolactone were examined. The effects of anhydride oligomers on polymer microsphere degradation, crystallinity, and surface morphology were also explored. The results demonstrated that fumaric anhydride oligomer remained within polymer microspheres for several hours after exposure to phosphate buffer, formed a homogenous crystalline blend, increased bioadhesion as measured on rat intestine, and enhanced drug delivery in vitro as measured by the everted sac technique.

Ring‐chain interactions in solutions of cyclic and linear poly(methylene) ester oligomers in p‐dioxan and chloroform

AbstractThe thermodynamic behavior of ternary solutions containing one cyclic (CYC10 and CYC20) and one linear (LIN10 and LIN20) poly(methylene) ester oligomer, respectively, in p‐dioxan and chloroform were investigated through vapor‐pressure measurements. Experiments were carried out at 25, 30, 35, and 40 °C. The ring‐chain interaction parameters χ″ were evaluated using the Leonard's equation for a ternary polymer solution containing one ring polymer. Results indicated that the values of χ″ are concentration and solvent dependent, and they vary with molecular size and slightly with temperature. All χ″ values were positive for both CYC10/LIN10 and CYC20/LIN20 blends, with the higher values for the former system, indicating that both ring‐chain oligomer blends are nearly immiscible, and the difference between cyclic and linear oligomers decreases as molecular size increases. The positive χ″ agrees with differential scanning calorimetric measurements performed on ring‐chain oligomer blends that show two distinct endotherms for the blends. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1425–1433, 2002