Bimodal Molar Mass Distribution Research Articles

Extraction and Characterization of Acidolysis Lignin from Turkey Oak (Quercus cerris L.) and Eucalypt (Eucalyptus camaldulensis Dehnh.) Wood from Population Stands in Italy.

Acidolysis lignins from the species Quercus cerris L. and Eucalyptus camaldulensis Dehnh. were isolated and characterized using high pressure size exclusion chromatography (HP-SEC), Fourier-transform (FTIR) infrared spectroscopy, analytical pyrolysis-gas chromatography-mass spectrometry (Py-GCMS), and two-dimensional heteronuclear single quantum coherence (2D HSQC) NMR spectroscopy. The acidolysis lignins from the two different species varied in chemical composition and structural characteristics, with Q. cerris L. lignin having a higher S/G ratio and higher molar mass averages with a bimodal molar mass distribution. The different analytical techniques FTIR spectroscopy, Py-GCMS, and 2D NMR spectroscopy provided consistent results regarding the S/G ratio of the lignins from the two wood species. Based on the determined high S/G ratio of both oak and eucalypt lignin, the two wood sources could be promoted as substrates for efficient lignin isolation in modern forest biorefineries in order to develop innovative lignin-based value-added biorefinery products.

Online hyphenation of size-exclusion chromatography and pyrolysis-gas chromatography for polymer characterization

An understanding of the composition and molecular heterogeneities of complex industrial polymers forms the basis of gaining control of the physical properties of materials. In the current work we report on the development of an online method to hyphenate liquid polymer chromatography with pyrolysis-GC (Py-GC). The designed workflow included a 10-port valve for fractionation of the first-dimension effluent. Collected fractions were transferred to the Py-GC by means of a second LC pump, a 6-port valve was used to control injection in the Py-GC, allowing the second pump to operate continuously. The optimized large volume injection (LVI) method was capable of analyzing 117 µL of the LC effluent in a 6 min GC separation with a total cycle time of 8.45 min. This resulted in a total run time of 2.1 h while obtaining 15 Py-GC runs over the molar mass separation.The method was demonstrated on various real-life samples including a complex industrial copolymer with a bimodal molar mass distribution. The developed method was used to monitor the relative concentration of 5 different monomers over the molar mass distribution. Furthermore, the molar mass-dependent distribution of a low abundant comonomer (styrene, <1% of total composition) was demonstrated, highlighting the low detection limits and increased resolving power of this approach over e.g. online NMR or IR spectroscopy. The developed method provides a flexible and widely applicable approach to LC-Py-GC hyphenation without having to resort to costly and specialized instrumentation.

Investigating the role of the different molar mass fractions of a pectin rich extract from onion towards its emulsifying and emulsion stabilizing potential

A pectin rich nitric acid extract produced from onion flesh (NA) showed promising emulsion stabilizing potential. At both pH 2.5 and pH 6.0, emulsions produced with the NA sample as sole emulsifying and emulsion stabilizing compound displayed stable oil droplet size distributions. Moreover, the emulsions showed good stability against creaming. Interestingly, the pectin rich acid extract was characterized by a bimodal molar mass distribution which led to the research objective to investigate the possible role of both polymer fractions in the promising emulsion stabilizing potential. To investigate this, both fractions were separated using centrifugal ultrafiltration.Structural characterization revealed the presence of mainly short chain galactans in the low molar mass fraction (NA-LMM) while the high molar mass fraction (NA-HMM) consisted mainly of pectin. Rheological analysis clearly demonstrated the viscosity increasing effect of NA-HMM in solution while the viscosity of a NA-LMM solution at equal concentration was comparable to pure water. Emulsions produced with NA-LMM destabilized quickly during refrigerated storage by extensive coalescence and creaming at pH 2.5. Despite presenting a somewhat better stability at pH 6, also in this case fast destabilization was observed. Contrarily, NA-HMM showed promising emulsion stabilizing potential. Oil droplet size distributions remained stable during storage at both pH 2.5 and pH 6.0. Creaming was observed for NA-HMM at pH 6.0 although to a lesser extent as for NA-LMM stabilized emulsions. Based on these results, it can be concluded that NA-LMM does not contribute to the emulsion stabilizing functionality of NA. Promising functionality is mainly attributed to the high molar mass polymers.

Structural and emulsion stabilizing properties of pectin rich extracts obtained from different botanical sources

The presented research studied the emulsifying and emulsion stabilizing capacity of pectin samples isolated from different plant origin: apple, carrot, onion and tomato. The acid extracted pectin samples showed distinct structural properties. Specifically, apple pectin showed a high degree of methylesterification (78.41 ± 0.83%), carrot pectin had the lowest concentration of other co-eluted cell wall polymers, onion pectin displayed a bimodal molar mass distribution suggesting two polymer fractions with different molar mass and tomato pectin was characterized by a high protein content (16.48 ± 0.05%). The evaluation of the emulsifying and emulsion stabilizing potential of the pectin samples included investigating their ability to lower the interfacial tension next to a storage stability study of pectin stabilized o/w emulsions. Creaming behavior as well as the evolution of the oil droplet size were thoroughly examined during storage using multiple analytical techniques. Overall, smaller oil droplet sizes were obtained at pH 2.5 compared to pH 6.0 indicating better emulsifying capacity at lower pH. The lowest emulsion stability was observed in emulsions formulated with tomato pectin in which weak flocculation and relatively fast creaming affected emulsion stability. Onion pectin clearly showed the most promising emulsifying and emulsion stabilizing potential. At both pH conditions, emulsions stabilized by the onion pectin sample displayed highly stable oil droplet sizes during the whole storage period. The presence of the two polymer fractions in this sample can play an important role in the observed stability. In future work, it could be evaluated if both fractions contribute to emulsion stability in a synergistic way. In conclusion, this work showed that pectin samples extracted from different plant origin display diverse structural properties resulting in varying emulsifying and emulsion stabilizing potential. Polymer molar mass potentially plays a major role in the structure-function relation.

Ti(IV)-Tris(phenolate) Catalyst Systems for the Ring-Opening Copolymerization of Cyclohexene Oxide and Carbon Dioxide.

Titanium(IV) complexes of amino-tris(phenolate) ligands (LTiX, X = chloride, isopropoxide) together with bis(triphenylphosphine)iminium chloride (PPNCl) are active catalyst systems for the ring-opening copolymerization of carbon dioxide and cyclohexene oxide. They show moderate activity, with turnover frequency values of ∼60 h–1 (0.02 mol % of catalyst, 80 °C, 40 bar of CO2) and high selectivity (carbonate linkages >90%), but their absolute performances are lower than those of the most active Ti(IV) catalyst systems. The reactions proceed with linear evolution of polycarbonate (PCHC) molar mass with epoxide conversion, consistent with controlled polymerizations, and evolve bimodal molar mass distributions of PCHC (up to Mn = 42 kg mol–1). The stoichiometric reaction between [LTiOiPr] and tetraphenylphosphonium chloride, PPh4Cl, allows isolation of the putative catalytic intermediate [LTi(OiPr)Cl]−, which is characterized using single-crystal X-ray diffraction techniques. The anionic titanium complex [LTi(OR)Cl]− is proposed as a model for the propagating alkoxide intermediates in the catalytic cycle.

Strontium Isopropoxide: A Highly Active Catalyst for the Ring-Opening Polymerization of Lactide and Various Lactones.

Commercially available strontium isopropoxide represents a suitable catalyst/initiator for the ring-opening polymerization (ROP) of lactide (LA), ε-caprolactone, δ-valerolactone, δ-caprolactone, and δ-decalactone. Well-defined polyesters are accessible via the solution polymerization of lactide in toluene with a [LA]:[Sr] ratio of 100:1 at room temperature with or without the addition of dodecanol as coinitiator. Kinetic studies and detailed analysis by means of matrix-assisted laser desorption ionization mass spectrometry reveal pseudo-first-order kinetics of the ROP as well as excellent endgroup fidelity of the polylactide (PLA) with isopropyl and dodecyl α-endgroups. Both isopropanolate moieties as well as the coinitiator each initiate PLA chains, enabling the synthesis of PLA with tailored molar mass. The polymerization of ε-caprolactone and δ-valerolactone confirms the high catalyst activity, which causes quantitative monomer conversion after 1 min polymerization time but broad molar mass distributions. In contrast, the catalyst is well suited for the ROP of the less reactive δ-caprolactone and δ-decalactone. Although kinetic studies reveal initially bimodal molar mass distributions, polyesters with dispersity values Ð < 1.2 and unimodal molar mass distributions can be obtained at moderate to high monomer conversions.

Molecular Dynamics Simulations of Short-Chain Branched Bimodal Polyethylene: Topological Characteristics and Mechanical Behavior

It has previously been shown that polyethylene (PE) with a bimodal molar mass distribution has a high fracture toughness. Our approach has been to use coarse-grained (CG) molecular dynamics (MD) simulations to investigate the effects of including short-chain branches in the high molar mass fraction of bimodal PE on topological features and mechanical behavior of the material. The CG potentials were derived, validated, and utilized to simulate melt equilibration, cooling, crystallization, and mechanical deformation. Crystallinity, tie chain, and entanglement concentrations were continuously monitored. During crystallization, the branched bimodal systems disentangled to a lesser degree and ended up with a higher entanglement density than the linear bimodal systems simulated in our previous study. The increase in entanglement concentration was proportional to the content of the branched high molar mass fraction. A significantly higher tie chain concentration was obtained in the short-chain branched bimodal s...

All-polyethylene composites reinforced via extended-chain UHMWPE nanostructure formation during melt processing

Nanophase separation during injection molding of high density polyethylene (HDPE) together with polyethylene reactor blend (RB) additives that have ultrabroad bimodal molar mass distribution and a high content of ultrahigh molar mass polyethylene (UHMWPE), produces thermoplastic all-polyethylene composites reinforced with extended-chain UHMWPE nanostructures formed in situ. Neither alien fibers, inorganic fillers, hazardous nanoparticles nor modified single- and multi-step molding processes are required to convert HDPE into higher performance engineering plastics. The RB40 additive is readily tailored by ethylene polymerization on silica-supported chromium two-site catalysts and contains 40 wt% UHMWPE (Mw = 1.5 × 106 g∙mol−1) dispersed in 50 wt% HDPE wax (Mw = 1.1 × 103 g∙mol−1). The presence of disentangled nanophase-separated UHMWPE together with HDPE wax serving as a processing aid enables injection molding of all-PE composites with high UHMWPE content of up to 24 wt% without changing processing parameters typical for HDPE. As verified by both scanning electron microscopic analyses of samples etched with hot xylene and thermal analysis, the HDPE matrix is efficiently reinforced by in situ formed polyethylene shish-kebab fibers where flow-induced crystallization yields extended-chain UHMWPE nanostructures as shish nucleating the crystallization of HDPE kebab. For the first time, by etching quenched samples, it was possible to completely suppress kebab formation and to image in situ extended-chain UHMWPE shish with an average diameter of 80 nm. Upon increasing the UHMPE content the average total diameter of shish-kebab fiber-like structures drastically decreases from micron to nanometer range, forming non-woven-like architectures. This self-reinforcement simultaneously improves toughness, stiffness and strength parameters unparalleled by conventional melt-blending HDPE with micron-sized UHMWPE and HDPE wax. Compared to HDPE, the addition of 60 wt% RB40 increases the Young's modulus to 4.2 GPa, tensile strength to 160 MPa and impact strength to 20 kJ/m2. This sustainable route to self-reinforced all-PE composite composites preserves the high energy, resource, cost and eco-efficiencies typical for pure hydrocarbon resins. Here, we examine the impact of RB40 addition on in situ nanostructure formation and its correlation with thermal and mechanical properties of all-PE composites.

Colloidal Dispersion of a Perfluorosulfonated Ionomer in Water⁻Methanol Mixtures.

We have investigated the dispersion state of a perfluorosulfonated ionomer (PFSI; Nafion®) in aqueous dispersion and the effect of methanol (MeOH) added to the aqueous dispersion by small-angle X-ray scattering (SAXS) as well as static and dynamic light scattering (SLS and DLS, respectively). Although both electrostatic and hydrophobic interactions of PFSI are expected to be strong in the dispersions, SAXS profiles obtained were satisfactorily fitted by the spherical particle model of a bimodal molar mass distribution. The rod-like aggregate model proposed in previous papers was denied at least for the present PFSI dispersion. Although the SAXS profiles exhibited a weak peak and the auto-correlation functions of DLS showed a log-time decay by the “repulsive cage effect” due to the long-ranged electrostatic interaction among PFSI particles, the concentration dependence of SLS results was probably normal because the cancellation of the electrostatic and hydrophobic interactions. The addition of MeOH into the aqueous dispersion of PFSI weakened both the hydrophobic and electcrostatic interactions of PFSI, and it is rather difficult to classify whether MeOH is a good or poor solvent (dispersant) for PFSI.

Tailored Nanostructured HDPE Wax/UHMWPE Reactor Blends as Additives for Melt-Processable All-Polyethylene Composites and in Situ UHMWPE Fiber Reinforcement

Tailored polyethylene reactor blend additives (RB) with ultrabroad bimodal molar mass distributions comprise nanophase-separated ultrahigh molar mass polyethylene (UHMWPE) uniformly dispersed in polyethylene wax. During injection molding of high-density polyethylene (HDPE) together with variable amounts of the nanophase-separated HDPE wax/UHMWPE (70/30) additive (RB30) flow-induced oriented crystallization affords shish-kebab fiber-like UHMWPE nanostructures accounting for efficient HDPE self-reinforcement. RB additives are readily prepared by ethylene polymerization on silica-supported two-site chromium catalysts which simultaneously produce HDPE wax together with disentangled nanoplatelet-like UHMWPE. The presence of HDPE wax is essential for lowering melt viscosity at high UHMWPE content. Since HDPE wax crystallizes onto extended-chain UHMWPE shish to form kebab structures, high HDPE wax content is tolerated without encountering emission problems and impairing mechanical properties as observed in the a...

Chemical modification of poly(lactic acid) and its use as matrix in poly(lactic acid) poly(butylene adipate-co-terephthalate) blends

Poly(lactic acid), PLA, was chemically modified with maleic anhydride (MA) by reactive extrusion. The effect of this modification on molar mass (MM) and acidity was assessed by means of size-exclusion chromatography (SEC) and titration, respectively. PLA MM decreased in the presence of MA solely and of MA and peroxide. Reduction in MM was monitored by the increase in acidity. PLA blends containing poly(butylene adipate-co-terephthalate) (PBAT) were prepared through different mixing protocols, PLA/PBAT, PLA-g-MA/PBAT and PLA/PBAT/MA/peroxide (PLA/PBAT in situ). SEC results and rheological properties revealed reduction in MM and viscosity of the modified blends. PLA/PBAT presented increase in MM and bimodal MM distribution. The calculated interfacial tension was significantly lower for the modified blends, despite the lower average particle area of PLA/PBAT. Surprisingly, the modified blends presented higher yield strength than that predicted by the rule of mixtures, which might indicate interfacial reactions.

Modeling of Polyolefin Polymerization in Semibatch Slurry Reactors: Experiments and Simulations

In this work, a well‐known single‐particle model (the multigrain model) is applied to simulate size growth and morphology evolution of polyethylene particles obtained through a slurry phase, catalytic polymerization in semibatch reactor. The model explicitly accounts for diffusion limitations within the polymer particle and between the particle and the solvent, as well as void fraction variations due to the particle growth. Catalyst behavior is described assuming a two‐site model, a good compromise between accuracy and simplicity, along with a conventional kinetic scheme, whose kinetic parameters are determined by fitting the model predictions to the experimental data. Polymer molecular weight is evaluated from population balances, solved through the method of moments. The semibatch reactor is modeled by means of fundamental mass conservation equations. Simulations show that the proposed model is able to describe not only the polymer properties of interest but also the evolution of the average particle size, thus providing a comprehensive overview of the system behavior. The model is further validated through regression‐free simulation of additional sets of experimental data, including materials with a bimodal molar mass distribution: the good agreement also found in this case confirms the robustness of the model and the estimated parameter values.image

The influence of molecular weight distribution of industrial polystyrene on its melt extensional and ultimate properties

We analyze the linear viscoelastic behavior and the strain‐rate dependence of nonlinear viscoelastic as well as the ultimate extensional properties of industrially relevant linear polystyrene mixtures (PS). The studied materials comprise different miscible binary mixtures of a well entangled matrix and unentangled diluent resulting in bimodal molar mass distribution (MWD). We also analyze the effect of the diluent weight average molar mass (Mw) by comparison with a mixture having broad but monomodal MWD. We show that the dilution effect on linear rheological properties is in agreement with the theoretical value of unity for the dilution exponent. We further show that the processing window, expressed as the ability of the material to withstand a given load without loss of homogeneity during elongation or ultimate loss of cohesion, is affected differently depending on the diluent Mw and concentration. Finally, we conclude that the existence of strain hardening is not sufficient for complete characterization of extension dominated operations. Our results demonstrate that significant enhancement of strain hardening achieved by adding small‐Mw diluents is often accompanied by trade‐off with respect to failure behavior of these mixtures. POLYM. ENG. SCI. 56:1012–1020, 2016. © 2016 Society of Plastics Engineers

Forensic engineering of advanced polymeric materials. Part III - Biodegradation of thermoformed rigid PLA packaging under industrial composting conditions

This paper presents a forensic engineering study on the biodegradation behaviour of prototype packaging thermoformed from PLA-extruded film and plain PLA film under industrial composting conditions. Hydrolytic degradation in water was conducted for reference. The effects of composting duration on changes in molar mass, glass transition temperature and degree of crystallinity of the polymeric material were monitored using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The chemical structure of water soluble degradation products of the polymeric material was determined using nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS). The results show that the biodegradation process is less dependent on the thermoforming process of PLA and more dependent on the composting/degradation conditions that are applied. The increase in the dispersity index, leading to the bimodal molar mass distribution profile, suggests an autocatalytic hydrolysis effect at the early stage of the composting process, during which the bulk hydrolysis mechanism dominantly operates. Both the prototype PLA-packaging and PLA rigid film samples were shown to have a gradual increase in opacity due to an increase in the degree of crystallinity.

Kinetics and monomer partitioning during polymerization of vinyl acetate in microemulsions stabilized with AOT and n-butanol

Vinyl acetate (VAc) was polymerized in microemulsion using sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as surfactant and n-butanol (n-BuOH) as the cosurfactant (1:1, wt/wt) with potassium persulfate (KPS) as initiator. The effects of monomer, surfactant, and initiator concentration, as well as the temperature on the kinetics, particle size, and molar masses were studied. It was observed that polymerization rate increases as monomer, initiator, and temperature increases; however, the opposite was observed as surfactant concentration increases. Average particle diameters (Dp) < 50 nm and polymers with weight average molar masses (Mw) between 2.7 × 105 and 7.5 × 105 g/mol were obtained. For low amounts of stabilizing agents (AOT and n-BuOH), a bimodal molar mass distribution (MMD) was obtained. As n-butanol concentration increased, Mw decreases and a monomodal MMD was observed, which can be explained because chain transfer events are promoted by the presence of n-BuOH. A thermodynamic model was implemented to simulate the partitioning of VAc in the presence of n-BuOH between the phases throughout polymerization. It was found from simulations that microemulsion droplets are depleted fast at 5 % conversion and, due to the high water solubility of VAc, most of the monomer (70 %) and n-BuOH (97 %) reside in the aqueous phase at the beginning of polymerization, which indicates that both homogeneous and micellar nucleation are present.

Influence of compositions and polymerization processes on morphologies, molar mass distributions, and phase structures of n‐Butyl acrylate–methyl methacrylate copolymers

ABSTRACTThe target of the research is to examine influence of a polymerization process and monomer ratio on structures and compositions of phases in an emulsion copolymerization of n‐butyl acrylate (BA) and methyl methacrylate (MMA). Emulsion copolymerizations are performed using three different BA/MMA weight ratios (60%/40%, 50%/50%, and 40%/60%) and two different processes, statistical batch and seeded emulsion polymerizations. Phase structures, monomer compositions, and morphological stabilities of copolymers are investigated by differential scanning calorimetry, 1H‐NMR, and scanning electron microscopy. Gel permeation chromatography is used to follow the changes in the molar mass distribution during syntheses. The gel content and backbiting level of end products are measured by extraction and 13C‐NMR, respectively. Copolymerizations give products with a bimodal molar mass distribution and three or two separate phases having different BA/MMA compositions. The morphological stability of particles decreases with the increasing BA fraction in the feed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41467.

Graphene-Supported Dual-Site Catalysts for Preparing Self-Reinforcing Polyethylene Reactor Blends Containing UHMWPE Nanoplatelets and in Situ UHMWPE Shish-Kebab Nanofibers

The catalytic ethylene polymerization on dual-site catalysts, supported on functionalized graphene, enables nanostructure formation in polyethylene reactor blends by in situ formation of uniformly dispersed ultrahigh molecular weight polyethylene (UHMWPE) nanoplatelets and in situ formed aligned UHMWPE shish-kebab nanofibers. For tailoring bimodal molar mass distributions, the quinolylsilylcyclopentadienylchromium(III) complex (Cr-1), producing UHMWPE with Mw > 3 × 106 g mol–1, is blended together with bisiminopyridine complexes of either chromium(III) (CrBIP), producing polyethylene (PE) wax (2 × 103 g mol–1), or iron(II) (FeBIP), producing PE with Mw = 2.0 × 105 g mol–1. Hence, the FeBIP/Cr-1 and CrBIP/Cr-1 molar ratios govern the PE/UHMWPE weight ratio without affecting the average molar mass of the individual PE fractions. In sharp contrast to conventional UHMWPE/PE reactor blends, the UHMWPE content is substantially increased up to 17 wt % without impairing melt processing. In the case of graphene-supported FeBIP/Cr-1, SEM and TEM analysis reveal that UHMWPE nanoplatelets are formed during polymerization. This is attributed to graphene-mediated mesoscopic shape replication. During injection molding, the UHMWPE nanoplatelets are transformed into aligned UHMWPE shish-kebab nanofibers, thus enabling efficient polyethylene matrix reinforcement.

Silica Nanofoam (NF) Supported Single- and Dual-Site Catalysts for Ethylene Polymerization with Morphology Control and Tailored Bimodal Molar Mass Distributions

Highly active single- and dual-site catalysts supported on silica nanofoams (NF) enable the control of both polyethylene (PE) morphology and tailoring of bimodal PE molar mass distribution in catalytic ethylene polymerization. In a templating process, aqueous polystyrene (PS) nano suspensions are mineralized and calcinated at 600 °C, thus producing NF with specific surface area of 1200 m2/g and average pore diameter varying between 20 and 80 nm. Mineralization of the aqueous PS nano suspensions in a water-in-oil emulsion affords spherical NF with average diameter of 40 μm and control of pore size. The methylalumoxane- (MAO-) tethered NF immobilizes single-site catalysts such as metallocene (nBuZr), bisiminopyridine iron(II) (Fe) and constrained geometry chinolyl cyclopentadienyl chromium(III) complexes (Cr-1). Immobilization of binary blends of Fe/Cr-1 and nBuZr/Cr-1 affords NF-supported dual-site catalysts. The catalyst activity, PE particle size and molecular weight distribution varies as a function of the NF pore size. Typically, macroporous NF (pore size of 75 nm) are effective supports for Cr-1, producing ultrahigh molecular weight polyethylene (UHMWPE, Mw > 106 g/mol). Dual -site catalysts such as nBuZr/Cr-1 on mesoporous NF (pore size of 20 nm) enable tailoring of bimodal PE molar mass distribution with UHMWPE content increasing with increasing Cr-1/nBuZr molar ratio.

Effect of Rubber Clone on Fatty Acid Composition and Properties of Air Dried Sheet

Properties of air dried sheet (ADS) made from four different clones of Hevea brasiliensis (BPM24, RRIM600, PR255 and PB235) were investigated. BPM24, RRIM600 and PR255 rubbers show a bimodal molar mass distribution (MMD) while PB235 rubber has quasi-unimodal molar mass distribution. It was found that ADS from rubber clone with bimodal MMD (BPM24, RRIM600 and PR255) displayed lower original plasticity (P0) but higher plasticity retention index (PRI). Those rubber samples with bimodal MMD show higher accelerated storage hardening test (ASHT) values than ADS from PB235. Within bimodal rubbers, ADS from PR255 displayed lower PRI and P than the 2 other clones, i.e. RRIM600 and BPM24. ADS made from BPM24 and RRIM600 presented similar fatty acid composition with 3 major fatty acids namely linoleic acid (C18:2), stearic acid (C18:0) and oleic acid (C18:1). In contrast, major fatty acids of ADS made from PR255 were linoleic acid (C18:2) and furan fatty acid. Moreover, ADS from PB235 showed the highest amount of furan fatty acid which confirmed the results of Liengprayoon et al. [1]. Relationship between mesostructure, fatty acids composition and ADS properties are discussed.

Isotactic Polystyrene Reactor Blends with Tailored Bimodal Molar Mass Distribution

Reactor blend formation of soluble highly isotactic polystyrene (iPS) enables tailoring of bimodal iPS molar mass distributions containing variable amounts of ultrahigh molar mass iPS (UHMWiPS). A key feature is the facile iPS molar mass control, achieved by homogeneous catalytic styrene polymerization on a MAO-activated titanium bisphenolate catalyst, using 1,9-decadiene as chain transfer agent. Whereas UHMWiPS (Mw of 947 000 g mol–1) is formed in the absence of the diene, the molar mass Mw increases from 191 000 to 482 000 g mol–1 with decreasing diene/styrene molar ratio. In a cascade of two parallel reactors, polymerizing styrene in the presence and the absence of diene, the mixing ratio of the resulting two iPS solutions governs the UHMWiPS content of the reactor blends (RB-2). Hence, the contents of iPS and UHMWiPS are varied without affecting the average molar mass of both blend components. In reactor blends (RB-1), produced in a single reactor with delayed diene injection, molar mass and polydispersity of iPS/UHMWiPS as well as molar mass of the iPS fraction and UHMWiPS depend on the diene/styrene molar ratio and the delay time of the diene injection. In this study, we investigate the influence of both iPS molar mass and iPS molar mass distributions on crystallization behavior and viscoelastic properties. The correlation of zero shear viscosity with the iPS molar mass exhibits scaling of 3.4, typical for linear polymer chains. Below 10 wt % UHMWiPS content, bimodal iPS molar mass distribution enhances processability by shear thinning.