Broad Molecular Weight Distribution Research Articles

Synthesis of basic amino acid-grafted lignin for use as a high-performance pigment dispersant

Lignin is a promising dispersant due to its hyperbranched polymer structure, low cost, renewability and abundant availability. However, its use is limited by its broad molecular weight distribution, inhomogeneity, and low content of hydrophilic functional groups. In this work, lignin was functionalized with alkaline amino acids (EHL-AA) to enhance water solubility and molecular weight uniformity. The results showed that EHL-AA significantly improved the dispersion of pigment Red 57:1 (P.R.57:1) in aqueous solutions, reducing the required dosage by 50 % compared to commercial small-molecule dispersants. Additionally, histidine modified lignin (EHL-His) exhibited superior stability for P.R.57:1 compared to commercial lignosulfonate (REAX 85A). Molecular dynamics simulations further revealed that showed that EHL-His had the highest electrostatic potential difference and the largest absolute value of negative ESP. The adsorption of EHL-His onto the P.R.57:1 surface followed the pseudo-second-order kinetic model and the Langmuir model, with EHL-His showing a higher Langmuir constant (b) than REAX 85A, indicating the strongest interaction with the pigment. In summary, this work advances pigment dispersion technology and promotes the high-value utilization of lignin.

Type of pectin affects the functionality of potato protein-pectin conjugates in emulsions

This study investigated the effect of the molecular structure of pectin on conjugate formation and its functionality in plant protein-based emulsions. For this purpose, high-methoxylated, low-methoxylated, amidated citrus pectin and their mixtures with potato protein were vacuum-dried at defined process conditions. The change in free amino groups, colour and molecular weight distribution assessed conjugation. The side reaction, such as pectin degradation, was monitored by the degree of methoxylation, galacturonic acid content and intrinsic viscosity. In addition, FT-IR and hydrophobicity measurements were performed to determine the changes in chemical structure due to the occurring reactions. The ζ-potential, solubility and oil droplet size reflected the functionality of the conjugated samples.The results confirm that, apart from the conjugation of protein and pectin, where the most significant decrease in free amino groups was obtained with an increasing degree of methoxylation or presence of amide groups, undesirable degradation of pectin occurring, resulting in a broad molecular weight distribution of the conjugate samples. The conjugate formation was the highest with amidated pectin. The FT-IR measurements confirmed the formation of Maillard conjugates. The FT-IR spectra showed a decrease in the intensity signals of amide I and amide II and the formation of new C–N bond maxima. In addition, the conjugation caused the shift of the protein's isoelectric point to the acidic environment, resulting in higher solubility and improved emulsion stability at the isoelectric point of the protein.Regarding emulsion stability, the conjugates with amidated pectin performed best and achieved the narrowest oil droplet size distribution over a wider pH range. Emulsion-stabilising properties of conjugates with high- and low-methoxylated pectin differed only slightly. To better understand the underlying mechanisms for emulsion stabilisation, future research will focus on the interfacial properties of the conjugates as determined by interfacial shear rheology and pendant drop analysis.

Hydrophilic Poly(meth)acrylates by Controlled Radical Branching Polymerization: Hyperbranching and Fragmentation.

Topology significantly impacts polymer properties and applications. Hyperbranched polymers (HBPs) synthesized via atom transfer radical polymerization (ATRP) using inimers typically exhibit broad molecular weight distributions and limited control over branching. Alternatively, copolymerization of inibramers (IB), such as α-chloro/bromo acrylates with vinyl monomers, yields HBPs with precise and uniform branching. Herein, we described the synthesis of hydrophilic HB polyacrylates in water by copolymerizing a water-soluble IB, oligo(ethylene oxide) methyl ether 2-bromoacrylate (OEOBA), with various hydrophilic acrylate comonomers. Visible-light-mediated controlled radical branching polymerization (CRBP) with dual catalysis using eosin Y (EY) and copper complexes resulted in HBPs with various molecular weights (M n = 38 000 to 170 000) and degrees of branching (2%-24%). Furthermore, the optimized conditions enabled the successful application of the OEOBA to synthesize linear-hyperbranched block copolymers and hyperbranched polymer protein hybrids (HB-PPH), demonstrating its potential to advance the synthesis of complex macromolecular architecture under environmentally benign conditions. Copolymerization of hydrophilic methacrylate monomer, oligo(ethylene oxide) methyl ether methacrylate (OEOMA500), and inibramer OEOBA was accompanied by fragmentation via β-carbon C-C bond scission and subsequent growth of polymer chains from the fragments. Furthermore, computational studies investigating the fragmentation depending on the IB and comonomer structure supported the experimental observations. This work expands the toolkit of water-soluble inibramers for CRBP and highlights the critical influence of the inibramer structure on reaction outcomes.

Equibiaxial elongation of entangled polyisobutylene melts: Experiments and theoretical predictions

Equibiaxial elongational deformations are omnipresent in polymer processing technologies. The challenge of generating well-controlled equibiaxial elongational deformations in the laboratory has, however, severely inhibited progress on understanding the rheology of polymeric liquids and other complex fluids in this flow. More recently, a novel technique known as continuous lubricated squeezing flow has been developed that allows for rheological measurements in equibiaxial elongational deformations. In the present study, we examine the rheological behavior of two entangled polyisobutylene (PIB) melts with different molecular weight distributions in constant strain rate equibiaxial elongation flows. These new data are compared with predictions from two molecular models for entangled polymer melts inspired by the idea that entanglements dominate the relaxation dynamics. One model is the discrete slip-link model (DSM), and the other is known as the Rolie Double Poly (RDP) model. For the PIB with a relatively narrow molecular weight distribution, the predictions of both models are in good agreement with experiments and the DSM gives nearly quantitative agreement. For the broad molecular weight distribution PIB, both the DSM and RDP model predict strain hardening, which is not observed in the experiments.

Low-Viscosity Route to High-Molecular-Weight Water-Soluble Polymers: Exploiting the Salt Sensitivity of Poly(N-acryloylmorpholine).

We report a new one-pot low-viscosity synthetic route to high molecular weight non-ionic water-soluble polymers based on polymerization-induced self-assembly (PISA). The RAFT aqueous dispersion polymerization of N-acryloylmorpholine (NAM) is conducted at 30 °C using a suitable redox initiator and a poly(2-hydroxyethyl acrylamide) (PHEAC) precursor in the presence of 0.60 M ammonium sulfate. This relatively low level of added electrolyte is sufficient to salt out the PNAM block, while steric stabilization is conferred by the relatively short salt-tolerant PHEAC block. A mean degree of polymerization (DP) of up to 6000 was targeted for the PNAM block, and high NAM conversions (>96%) were obtained in all cases. On dilution with deionized water, the as-synthesized sterically stabilized particles undergo dissociation to afford molecularly dissolved chains, as judged by dynamic light scattering and 1H NMR spectroscopy studies. DMF GPC analysis confirmed a high chain extension efficiency for the PHEAC precursor, but relatively broad molecular weight distributions were observed for the PHEAC-PNAM diblock copolymer chains (Mw/Mn > 1.9). This has been observed for many other PISA formulations when targeting high core-forming block DPs and is tentatively attributed to chain transfer to polymer, which is well known for polyacrylamide-based polymers. In fact, relatively high dispersities are actually desirable if such copolymers are to be used as viscosity modifiers because solution viscosity correlates closely with Mw. Static light scattering studies were also conducted, with a Zimm plot indicating an absolute Mw of approximately 2.5 × 106 g mol-1 when targeting a PNAM DP of 6000. Finally, it is emphasized that targeting such high DPs leads to a sulfur content for this latter formulation of just 23 ppm, which minimizes the cost, color, and malodor associated with the organosulfur RAFT agent.

Development of Novel Star-Like Branched-Chain Acrylamide (AM)-Sodium Styrene Sulfonate (SSS) Copolymers for Heavy Oil Emulsion Viscosity Reduction and Its Potential Application in Enhanced Oil Recovery.

Injecting water with chemicals to generate emulsions in the reservoir is a promising method for enhancing heavy oil recovery because oil-in-water (O/W) emulsions significantly reduce oil viscosity. To enhance heavy oil recovery efficiency, we developed new star-like branched AM-SSS copolymers (SB-PAMs) with reduction in the viscosity of the heavy oil emulsion, which was synthesized by reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization. The core structure of the branched polymer was RAFT polymerization of acrylamide (AM) and N,N'-methylene bis-acrylamide (BisAM), in the presence of 3-(((benzylthio)carbonothioyl)thio)propanoic acid as a chain transfer agent, followed by chain extension with AM and SSS. The core structures were achieved by incorporation of total monomer ratios [BisAM]/[AM] of 1:11. The expansion of the core structures by copolymerization of AM and SSS resulted in star-like branched polymer SB-PAM-co-SSS with apparent molecular weights ranging from 240 to 2381 kDa. 1H-nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FTIR) confirmed the synthesized polymer structure. The molecular weight was determined by gel permeation chromatography (GPC). The polydispersity coefficient was between 1 and 7, which has a broad molecular weight distribution. The polymer dissolves only 0.75 h in deionized water, faster than conventional polyacrylamide. At 50 °C, the viscosity of the 1000 mg/L SB-polymer solution can reach up to 45 mPa·s. First, heavy oil viscosity reduction by 800 mg/L SB polymer can reach 91.7%, at a water dehydration rate of 90.4%; second, with 0.6 PV injection, 800 mg/L SB polymer improved oil recovery up to 23.66% after water flooding; and third, SB-polymer-assisted hot water flooding shows that heavy oil recovery improved by 19.46% at 110 °C with 0.6 pore volume (PV) SB-polymer injection. This novel branched chain polymer with heavy oil emulsion capability will shed light on high-temperature polymer flooding and the development of a new candidate structure for heavy oil viscosity reduction.

Well‐defined poly(N,N‐dimethylacrylamide) from a fast Cu(0)‐mediated reversible‐deactivation radical polymerization in water

AbstractCopper‐catalyzed reversible deactivation radical polymerization (RDRP) of N,N‐dimethylacrylamide (DMA) has been a significant challenge, particularly in aqueous environments, such as low yields, broad molecular weight distribution (MWD), and ill‐controlled molecular weights (MWs). In this work, we report the synthesis of well‐defined poly(N,N‐dimethylacrylamide) (PDMA) via a facile Cu(0)‐mediated RDRP in water. The results show that, unlike other acrylamide monomers, for DMA with abundant tertiary amide groups, the sufficient deactivation—the key to realizing control in copper‐catalyzed RDRP—cannot be simply fulfilled by just increasing the amount of deactivator (i.e., CuII species). The enhanced deactivation must be appropriately determined by also considering and selecting other reaction parameters. It is demonstrated that the use of methyl 2‐chloropropionate (MCP) as initiator and copper(II) chloride (CuCl2) as the additional catalyst is an effective combination to simultaneously enhance the deactivation control and facilitate the chain growth in aqueous Cu(0)‐mediated RDRP of DMA. This strategy successfully achieved the fast and well‐controlled synthesis of PDMAs with high monomer conversion, narrow MWDs, and a range of predefined MWs, and the well‐controlled in situ chain extensions.

Size Fractionation of Milliliter DNA Samples in Minutes Controlled by an Electric Field of ∼10 V.

DNA size fractionation is an essential tool in molecular biology and is used to isolate targets in a mixture characterized by a broad molecular-weight distribution. Microfluidics was thought to provide the opportunity to create devices capable of enhancing and speeding up the classical fractionation processes. However, this conjecture met limited success due to the low mass or volume throughput of these technologies. We describe the μLAF (μ-laboratory for DNA fractionation) technology for DNA size selection based on the stacking of molecules on films of ∼100 μm in thickness with 105 cm-2 pores ∼2 μm in diameter. Size selection is achieved by controlling the regime of electrohydrodynamic migration through the temporal modulation of an electric field. This technology allows the processing of milliliter-scale samples containing a DNA mass of several hundreds of ng within ∼10 min and the selection of DNA in virtually any size window spanning 200 to 1000 bp. We demonstrate that one operation suffices to fractionate sheared genomic DNA in up to six fractions with collection efficiencies of ∼20-40% and enrichment factors of ∼1.5-3-fold. These performances compare favorably in terms of speed and versatility to those of the current standards.

Processing of hemicellulose in wheat straw by steaming and ultrafiltration – A novel approach

Water-soluble xylans useable for many potential applications can be produced based on the hydrolysis of wheat straw within a fixed bed using saturated steam to provide a xylan-rich hydrolysate low in particles and lignin enabling an effective ultrafiltration and xylan separation. Under defined conditions (180 °C, 10 bar, 35 min), a degree of solubilization of 29.6 % for straw and of 63 % for hemicellulose is achieved. The dry mass of the resulting hydrolysate consists of at least 58 % xylose and arabinose. The xylose is mainly (87 %) present in non-monomeric form and appears to have a broad molecular weight distribution. Ultrafiltration with commercial membranes (4 to 50 kDa) is being investigated for the separation of the target fraction; here significant differences in the filtration behavior and rejections from 9 to 81 % for carbohydrates and from 13 to 48 % for phenolic compounds (lignin), respectively, are found.

Effect of molecular weight and its modality on pressure-sensitive adhesives behavior of plant oil-based latexes

Semibatch emulsion polymerization of high oleic soybean oil-based monomer (HO-SBM), 2–ethylhexyl acrylate (2-EHA), and styrene (St) was applied to synthesize pressure-sensitive latex adhesives with up to 40 wt% of plant oil-based content. Ternary latex copolymers with similar chemical composition and broadly different molecular weight distribution (MWD) and modality were synthesized at varying temperatures and the mechanism of free-radical initiation. Conventional thermal initiation with ammonium persulphate at 80 °C and ascorbic acid/tert-butyl hydroperoxide redox system of lower reaction temperature up to 20 °C were employed. Linear, short-chain, and long-chain branched macromolecules are formed due to chain-breaking reactions of HO-SBM (chain transfer on allyl groups) and 2-EHA (inter- and intramolecular chain transfer on the polymer). The dominant effect of chain transfer on allyl group protons and subsequent decrease in molecular weight was observed at higher reaction temperatures, while extensively branched polymer with high molecular weight was obtained at reaction temperature close to 20 °C.The effect of MWD and branching on the PSAs performance of synthesized biobased latexes was studied using loop tack and peel strength and lap shear testing and compared to two commercial PSA tapes as a benchmark. A significant increase in shear strength (up to 0.23 MPa) was observed for latex adhesives due to high molecular weight fractions, maintaining satisfactory level of tack (3–7 N) and peel (3–6 N/in). Broad MWD of the copolymers can be beneficial for providing materials with high shear strength (0.25–0.33 MPA) while preserving the significant level of tack (2–4 N) and peel strength (9–12 N/in) on both glass and steel substrates.

Research on the Impact of Deep Eutectic Solvent and Hot-Water Extraction Methods on the Structure of Polygonatum sibiricum Polysaccharides.

Deep eutectic solvent (DES) and hot-water extraction (HWE) methods were utilized to extract polysaccharides from Polygonatum sibiricum, referred to as DPsP and WPsP, respectively. The extracted polysaccharides were purified using the Superdex-200 dextran gel purification system, resulting in three components for each type of polysaccharide. The structures of these components were characterized. The molecular weight analysis revealed that DPsP components had slightly larger molecular weights compared with WPsP, with DPsP-A showing a slightly higher dispersity index and broader molecular weight distribution. The main monosaccharide components of both DPsP and WPsP were mannose and glucose, while DPsP exhibited a slightly greater variety of sugar components compared with WPsP. FTIR analysis demonstrated characteristic polysaccharide absorption peaks in all six PSP components, with a predominance of acidic pyranose sugars. NMR analysis revealed the presence of pyranose sugars, including rhamnose and sugar aldehyde acids, in both DPsP-B and WPsP-A. DPsP-B primarily exhibited β-type glycosidic linkages, while WPsP-A predominantly displayed α-type glycosidic linkages, with a smaller fraction being β-type. These findings indicated differences in monosaccharide composition and structure between PSPs extracted using different methods. Overall, this study provided experimental evidence for future research on the structure-function relationship of PSPs.

Azobenzene-Containing Liquid Crystalline Twisted Ribbons via Polymerization-Induced Hierarchical Self-Assembly.

Polymerization-induced self-assembly incorporating liquid crystallization, as a polymerization-induced hierarchical self-assembly (PIHSA) method to produce polymeric particles with anisotropic morphologies facilely and efficiently, has drawn wide attention recently. However, the means of regulating the morphologies of liquid crystalline (LC) polymer assemblies still need to be explored. Herein, a route is presented to fabricate the twisted ribbons via PIHSA containing azobenzene based on poor reversible addition-fragmentation chain transfer (RAFT) control, called poorly controlled PIHSA. Cyano-4-(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid-2-(2-pyridyldithio) ethyl ester is used as the RAFT agent with poor controllability, and the morphological evolution from ribbons to twisted ribbons can be observed in the corresponding PIHSA system. The formation mechanism of the twisted ribbons is studied systematically and the broad molecular weight distribution is considered to be the decisive factor. Moreover, the supramolecular chirality induced by symmetry breaking is also related to the twist of the ribbons. This study enriches the methods of controlling the morphologies of LC polymer particles and is helpful for further clarifying the mechanism of PIHSA.

Controlled Polymerization of Acrylamide via One-Pot and One-Step Aqueous Cu(0)-Mediated Reversible-Deactivation Radical Polymerization.

Copper-catalyzed controlled polymerization of acrylamide (AM) has always been a challenge, which typically exhibits low monomer conversion and broad molecular weight distribution (MWD) or requires complex/multistep reaction procedures, due to the highly active nature of the AM radical and its side reactions. To overcome the above challenges, herein, we report the successful synthesis of well-defined polyacrylamide (PAM) via a facile one-pot and one-step aqueous Cu(0)-mediated reversible-deactivation radical polymerization (RDRP). The results of this strategy show that strong deactivation control is the key for the controllability of AM RDRPs, which depends on the equilibria of polymerization and mutual conversion of different copper species. With the fast-propagating monomer AM, extra addition of CuII into the reaction system is an effective way to enhance deactivation. Based on this kinetically controlled strategy, well-defined PAMs with narrow molecular weight distributions (MWDs) and varied molecular weights (Mws) were successfully achieved.

Extraction, Composition, Functionality, and Utilization of Brewer’s Spent Grain Protein in Food Formulations

In recent years, brewer's spent grain (BSG) has gained attention as a plant-based protein source because it occurs in large quantities as a by-product of beer brewing. BSG can contribute to future food requirements and support the development of a circular economy. In light of the dynamic developments in this area, this review aims to understand the proteins present in BSG, and the effect of extraction techniques and conditions on the composition, physicochemical, and techno-functional properties of the obtained protein extracts. The water-insoluble hordeins and glutelins form the major protein fractions in BSG. Depending on the beer brewing process, the extraction technique, and conditions, the BSG protein isolates predominantly contain B, C, and ϒ hordeins, and exhibit a broad molecular weight distribution ranging between <5 kDa and >250 kDa. While the BSG isolates obtained through chemical extraction methods seem promising to obtain gelled food products, physical and enzymatic modifications of BSG proteins through ultrasound and proteolytic hydrolysis offer an effective way to produce soluble and functional protein isolates with good emulsifying and foaming capabilities. Specifically tailored protein extracts to suit different applications can thus be obtained from BSG, highlighting that it is a highly valuable protein source.

A New Optimization Strategy of Highly Branched Poly(β-Amino Ester) for Enhanced Gene Delivery: Removal of Small Molecular Weight Components

Highly branched poly(β-amino ester) (HPAE) has become one of the most promising non-viral gene delivery vector candidates. When compared to other gene delivery vectors, HPAE has a broad molecular weight distribution (MWD). Despite significant efforts to optimize HPAE targeting enhanced gene delivery, the effect of different molecular weight (MW) components on transfection has rarely been studied. In this work, a new structural optimization strategy was proposed targeting enhanced HPAE gene transfection. A series of HPAE with different MW components was obtained through a stepwise precipitation approach and applied to plasmid DNA delivery. It was demonstrated that the removal of small MW components from the original HPAE structure could significantly enhance its transfection performance (e.g., GFP expression increased 7 folds at w/w of 10/1). The universality of this strategy was proven by extending it to varying HPAE systems with different MWs and different branching degrees, where the transfection performance exhibited an even magnitude enhancement after removing small MW portions. This work opened a new avenue for developing high-efficiency HPAE gene delivery vectors and provided new insights into the understanding of the HPAE structure-property relationship, which would facilitate the translation of HPAEs in gene therapy clinical applications.

Dibenzosuberyl substituents suppressing chain transfer in Bis(imino)pyridyl Iron(II) catalyzed ethylene polymerization

It is an efficient way to introduce ortho-aryl dibenzosuberyl substituents into late-transition metal catalysts for retarding chain transfer in olefin polymerization. Here, we further found that dibenzosuberyl substituents could also suppress chain transfer and thus increase the molecular weight in ethylene polymerization with bis(imino)pyridyl Fe(II) catalysts. A series of bis(imino)pyridyl ligands with unilateral diarylmethyl or dibenzosuberyl moiety on the ortho-positions of N-aryl rings and their corresponding Fe(II) catalysts were synthesized and characterized. All these bis(imino)pyridyl Fe(II) catalysts exhibited high polymerization activity and could generate high weight-average molecular weight polyethylenes with very broad molecular weight distributions in most cases. Among them, the dibenzosuberyl Fe(II) catalysts could generate ultra-high weight-average molecular weight (Mw = 2038–2137 kg/mol) polyethylenes at low temperatures, significantly higher than the diarylmethyl catalysts. The obtained polyethylenes are all highly linear with almost no branching distribution.

Microwave dielectric heating affects the in‐situ polymerization process of Nylon‐6/Ag‐NPs hybrid polymer nanocomposite

AbstractIn this work, the microwave synthesis of Nylon‐6 hybrid polymeric nanocomposite (HPNC) was studied by the polymerization of ε‐caprolactam, 6‐aminocaproic acid, and 2% wt of silver nanoparticles (Ag‐NPs). It was determined that the dielectric heating (DH) of the Ag‐NPs controls the thermal behavior of the HPNCs synthesis and triggers the chemical reaction between Ag‐NPs and the Nylon‐6 molecules. Such reaction promotes their coating with the polymer and their precipitation, which affects the agitation of the reaction mixture, and results in broader molecular weight distribution and three HPNC populations. Usually, the power output effect in these processes is thermal as it accelerates their heating rate. Still, for HPNCs, higher output reduces the agglomerate size of the Ag‐NPs and accelerates their precipitation. At power up to 600 W, the DH of the Ag‐NPs causes the explosion of the reaction vials. The antimicrobial activity of the HPNCs against P. aeruginosa is almost 100% effective at 180 min of exposure; therefore, this microwave synthesis process is suitable for producing antimicrobial HPNCs.

Enhanced Performance of Lignin Recovery with a Carbon Dioxide Acidification Method.

Lignin particles were recovered from the bagasse soda pulping black liquor by acidification with carbon dioxide continuously fed in a semibatch reactor. An experimental model based on the response surface methodology was selected to investigate the effect of parameters and optimize the process for maximizing the lignin yield, and the physicochemical properties of the obtained lignin under the optimum conditions were investigated for further potential applications. A total of 15 experimental runs of three controlled parameters including temperature, pressure, and residence time were carried out based on the Box-Behnken design (BBD). The mathematic model for lignin yield prediction was successfully estimated at 99.7% accuracy. Temperature played a more significant role in lignin yield than pressure and residence time. Higher temperature could faciltate a higher lignin yield. Approximately 85 wt % lignin yield was obtained under the optimum conditions with a purity higher than 90%, high thermal stability, and slightly broad molecular weight distribution. The p-hydroxyphenyl-guaiacyl-syringyl (HGS)-type lignin structure and spherical shape were confirmed by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM). These characteristics confirmed that the obtained lignin could be used in high-value products. Moreover, this work indicated that the CO2 acidification unit for lignin recovery could be efficiently improved for achieving high yield and purity from black liquor by adjustment of the process.

Porous Organic Polymers-Supported Zeigler-Natta Catalysts for Preparing Highly Isotactic Polypropylene with Broad Molecular Weight Distribution.

Porous organic polymers (POPs) have attracted much attention in numerous areas, including catalysis, adsorption and separation. Herein, POP supported Ziegler-Natta catalysts were designed for preparation of isotactic polypropylene (iPP). The POPs-based Ziegler-Natta catalysts exhibited the characteristic of broad molecular weight distribution (MWD > 11) with or without adding an extra internal electron donor. The added internal electron donor 3-methyl-5-tert-butyl-1,2-phenylene dibenzoate (ID-2) used in cat-2 showed good propylene polymerization activity of 15.3 × 106 g·PP/mol·Ti·h, high stereoregularity with 98.2% of isotacticity index and broad molecular weight distribution (MWD) of 12.3. Compared to the MgCl2-supported Ziegler-Natta catalysts (cat-4) with the same ID-2, cat-2 showed higher chain stereoregularity for propylene polymerization. As seen in the TREF results, the elution peak of PP-2 (124.0 °C, 91.7%) is 1.5 °C higher than the isotactic fraction from PP-4 (122.5 °C, 87.2%), and even 1.2 °C higher than PP-5 prepared from ID-3 with the characteristics of high stereoregularity. Moreover, the pentad methyl sequence mmmm of PP-2 (93.0%) from cat-2 is 0.5% higher than that of PP-4 from cat-4. XPS analysis revealed that the minute difference in binding energy of Ti, Mg, C and O atoms exist between the inorganic MgCl2 and the organic polymer based Z-N catalysts. The plausible interaction mechanism of active sites of Mg and Ti with the functional groups in the POP support and the added ID was proposed, which could be explained by their high stereoregularity and the broad molecular weight distribution of the POP-based Z-N catalysts.

Insight of polypropylene synthesis with high performance multidentate internal donor catalyst system

AbstractPropylene polymerization using magnesium dichloride (MgCl2) supported Ziegler–Natta (Z–N) system is a robust and preferred catalytic process for producing polypropylene (PP) grades. Herein, synthesis of polypropylene products is reported using MgCl2 supported multidentate (3,3,3′,3′‐tetramethyl‐2,2′,3,3′‐tetrahydro‐1,1′‐spirobiindane‐5,5′,6,6′‐tetracarbonate) Z–N pre‐catalyst. The catalyst performance evaluation over propylene polymerization found that multidentate Z–N pre‐catalyst has better hydrogen response with controlled isotacticity of PP products as compared to conventional bidentate Z–N pre‐catalysts. Melt rheology analysis showed higher loss modulus and storage modulus for ultra‐high molecular weight isotactic polypropylene (UHMWiPP) as compared to PP resins with medium molecular weight. Further, GPC analysis reveal medium to broad unimodal molecular weight distribution (MWD) of PP products produced with multidentate Z–N pre‐catalyst system.