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An approach is described for the synthesis of controlled submicron interpenetrating networks with distinct functional features in commodity polymers, based on a mechanism of crazing and polymerization. In this work, ion conductivity was introduced into polyethylene with only minor losses in its mechanical properties, using a highly branched acrylic hydrogel. Control over the porous network developed in the matrix was gained by the addition of a crystallizing nucleating agent, which was used to increase the number and reduce the size of crystallites. Variation of experimental conditions, such as the degree of elongation and applied reaction pressure, produced different morphologies and conductivity for the co-continuous alloy. The samples were deformed in a liquid medium that possessed an affinity for the matrix material, and acted both as a surface-active agent for the crazing, and as a reactant for the conductive phase. Without pressure, deforming by 100% strain yielded a conductivity of 5.67×10⁻⁷ S/cm for the polymer specimen. Simultaneously increasing system pressure while constantly straining a specimen enabled further enhancements in conductivity. As a particular example, elongation of 100% and applied pressure up to 2.76 MPa ensured conductivity nearly equal to that of the pure hydrogel at 4.43×10⁻⁴ S/cm. NSERC

This work reports a novel type of reversible shape memory polymers (RSMPs) from commercially available thermoplastic polyolefin elastomers (POEs). Two RSMPs based on Dow Chemical’s POE Engage 8003, Engage 8137, Engage 8180, and olefin block copolymer elastomer Infuse 9007 were prepared by simple blending of the commercial products having different melting temperatures. The multiple and reversible shape memory performances of the as-prepared blends were clearly demonstrated. This work provides a facile and low-cost method for the large-scale preparation of the reversible shape memory materials. It broadens the source of the materials for the design and development of RSMPs.

The tactics of targeting copolymer composition (CC) and molecular weight (MW) via semibatch controlled radical polymerization (CRP) have been extensively studied. However, little effort is made to target copolymer sequence length (CSL) and its triad sequence, which are among the key microstructures determining material properties of the copolymers. This work presents a method to design and synthesize targeted CSL and copolymer triads in a reversible addition–fragmentation chain transfer radical mini-emulsion copolymerization system (RAFT) through a semibatch chain and sequence model coupled with Alfrey Mayo model. The kinetic model was first derived and correlated with experimental results of the batch St/BA copolymerizations. The semibatch RAFT model was then employed to calculate the feed-rate to target CSL and their triads. St/BA copolymers with different uniform CSLs and their triads are synthesized through the programmed semibatch RAFT mini-emulsion copolymerization processes.

This work reports the preparation of a novel class of lignin reverse micelles (LRM) and their application as a UV-blocking additive for thermoplastics. It is found that when 7 vol % cyclohexane was added into alkali lignin (AL)/dioxane solution, LRM formed. When the cyclohexane amount increased, LRM tended to aggregate and separate from the solutions. LRM films had a water contact angle higher than 80°, in comparison to only 52° of the AL film control sample. Due to hydrophobicity, the miscibility of LRM with high density polyethylene (HDPE) was significantly improved from that of AL with HDPE. Since LRM retained the phenolic hydroxyl structure of AL, the HDPE/LRM samples showed an excellent UV-absorbing performance. Furthermore, the added LRM had little negative influence, but significantly improved the HDPE mechanical properties. With 5 wt % LRM loading, Young’s modulus increased from 1066 to 2104 MPa and the elongation at break increased from 671% to 1030%, respectively.

Some commercially available amines used as curing agents for epoxy resins can capture CO2 to form ammonium carbamates, which represent a novel type of latent blowing and curing agent for epoxy foaming. The principles in the selection of suitable amines are critical for final applications. This work aimed to reveal these principles by screening and comparing the preparation, chemical structure and composition, and curing and foaming performance of several types of ammonium carbamates from typical amine curing agents. It is found that amines with pKa >9 are eligible to react with CO2 to form ammonium carbamates with a high yield. Furthermore, the amines should have rigid cyclic groups in their structures to form a solid ammonium carbamate powder, which can be easily mixed with epoxy resins. The curing rate of the amine should not be much faster than the decomposition of the carbamate to obtain epoxy foams with good pore morphology and mechanical performance.

The separation of natural homologues provides a great challenge due to high similarities of their structures and properties. In this work, the use of the polymeric extractant polyethylenimine (PEI) for the separation of α-tocopherol from the tocopherol homologues was investigated. Various PEI–cosolvent solutions were used to extract tocopherols from their hexane solutions. The effects of PEI molecular weight, cosolvent type, and PEI–cosolvent composition were systematically studied. High distribution and selectivity coefficients of tocopherols were obtained with PEI–acrylonitrile (ACN) as the extractant. A clear advantage of PEI extractant is its stimuli-responsive property triggered by CO2. PEI–extracted tocopherols could be replaced and released from PEI chains with CO2 bubbling, with PEI–CO2 precipitated out from the extract phase, which greatly facilitates the back extraction of tocopherols and the recovery of PEI for reuse. With CO2 bubbling, it took only three back extractions to recover over 90% to...

Copolymer composition distribution (CCD) is an important parameter of chain microstructure that has significant impact on the material properties of polymer products. Controlled/living radical poly...

Methyl methacrylate (MMA) was polymerized in bulk via atom transfer radical polymerization (ATRP) with azobis(isobutyronitrile) (AIBN) and tert-butyl peroxybenzoate (TBPB) as initiator for continuous activator regeneration (ICAR). The ATRP was first carried out up to high conversion at 70 °C. When the system reached its glass state at about 94%, the polymerization temperature was elevated to 120 °C to maximize the conversion. Livingness of the ICAR ATRP process and control of polymer molecular weight at high conversion were carefully examined to elucidate the mechanisms of diffusion-controlled reactions. The “gel effect” started at about 50% conversion, and it was accompanied by molecular weight distribution broadening. A dramatic increase in polydispersity was observed at above 90% conversion. The loss of control over molecular weight was caused by diffusion-controlled deactivation, which could be reduced to some extent by increasing deactivator concentration. However, despite the loss of control at high...

Polypropylene/ethylene−propylene rubber (PP/EPR) reactor alloys were prepared with a metallocene/Ziegler−Natta hybrid catalyst system (rac-Et(Ind)2ZrCl2/TiCl4/MgCl2) using a process composed of three stages: propylene homopolymerization, metallocene activation, and ethylene−propylene copolymerization. A series of alloy samples were produced and characterized at various copolymerization conditions by varying the methylaluminoxane (MAO)/Zr ratio and monomer composition. It was shown that the metallocene/Ziegler−Natta hybrid system exhibited the features of both metallocene and Ziegler−Natta catalysts during copolymerization. The hybrid catalyst had better ability in incorporating α-olefin than the Ziegler−Natta catalyst owing to the action of metallocene active sites. DSC and IR analyses suggested that EPR in the alloys became random with increased MAO/Zr ratio. In addition, reducing the ethylene content in the feed decreased the activity and promoted the production of random copolymers. An operation window...

The ionic liquid 1,1,3,3-tetramethylguanidinium lactate (TMGL) was supported onto porous silica particles via a facile impregnation−vaporization method. The TMGL-supported particles gave high porosity and large specific surface area. The SO2 sorption/desorption properties of the silica-supported TMGL (TMGL−SiO2) were evaluated, and high SO2 sorption capacity and rate were achieved. Its capacity reached 0.6 g SO2/g TMGL in 15−30 min with pure SO2 gas and 0.15 g SO2/g TMGL in 17 h with a N2/SO2 mixture gas that contained 2160 ppm SO2. The SO2 concentration was reduced to 12.6 ppm after sorption. The TMGL−SiO2 system could be reused for many sorption/desorption cycles without change in its capacity. It was also characterized by good mechanical strength and thermal stability at temperature up to 130 °C. The SO2 sorbent system appears to be useful in gas desulfurization.

Ethylene-1-hexene copolymers were synthesized with a tandem catalysis system consisting of a new trimerization catalyst (1), bis(2-dodecylsulfanylethyl)amine-CrCl3, and a copolymerization catalyst (2), Et(Ind) 2 ZrCl 2 . Catalysts 1 and 2 were supported on silica particles, and the effects of different supporting strategies on trimerization selectivity, 1-hexene incorporation efficiency, and copolymerization activity were studied and compared to the homogeneous system. It was found that the supported 1 trimerized ethylene with a similar selectivity (>99%) but one-quarter of the activity of the homogeneous 1. The supported 2 gave 40% 1-hexene incorporation efficiency and one-third of the copolymerization activity of the homogeneous 2. The tandem action of the supported 1 and 2 yielded linear low-density polyethylene (LLDPE) materials that contained only C4 side-chains. The dual supported system had activities at a 10 7 g/(mol Zr h) level, in the same order of the homogeneous counterpart. Adjusting the Cr/Zr ratio yielded various branching densities and, thus, melting temperatures of the resulting polymers. The samples prepared with the supported 2 exhibited broad differential scanning calorimetry (DSC) curves, probably due to multiple active sites.

Shirasu porous glass (SPG) membrane emulsification has many advantages over traditional emulsification methods of stirring, ultrasoubd, and homogenization. The main advantages are much improved uniform size distribution of the droplets and lower mechanical shear stress. This paper examines the uniformity and stability of sunflower oil emulsions prepared by SPG membrane. The effects of emulsifiers on the uniformity and stability of emulsions were investigated. Results showed that emulsions stabilized by Tween 20 are generally more uniform and stable compared to those stabilized by Tween 60. Emulsions prepared by membrane emulsification showed excellent uniformity and stability with no droplet size change after 6-months storage, while those prepared by the homogenizer have a much broad size distribution and are unstable after 7 days of storage with significant further broadening of the droplet size distribution by coalescence and Oswald ripening. Uniform-sized sunflower O/W emulsions prepared by the SPG membrane also have good thermal stability when subjected to either freezing or heating. The mechanical stability of sunflower O/W emulsions prepared by the SPG membrane can be further improved by adding thickeners to the aqueous phase. Therefore, SPG membrane emulsification is a promising method for preparing uniform and stable emulsions, which will have good potential applications in the food industry, in terms of improving shelf life and product quality.

The solubilities of heterogeneous atom transfer radical polymerization (ATRP) catalysts are determined for the first time and used to calculate previously unquantified ATRP equilibrium constants (KATRP). These new data are essential for understanding, modeling, and designing ATRP processes with low catalyst concentrations. KATRP values for CuIBr/1,1,4,7,10,10-hexamethyltriethylenetetramine (CuIBr/HMTETA) and CuIBr/N,N,N‘,N‘,N‘ ‘-pentamethyldiethylenetriamine (CuIBr/PMDETA) are 8.66 × 10-6 and 1.44 × 10-6, respectively. The limited solubility of the CuIBr/HMTETA catalyst explains why large reductions in metal salt concentration can be made without affecting polymerization rates. Catalyst solubility and polymerization rate increase with ligand concentration. In contrast, increasing the metal salt concentration in excess of the ligand's causes a drop in catalyst solubility. This unexpected observation is attributed to the formation of insoluble catalyst networks (gels). The solubility data point to differenc...

Chain walking polymerization provides a novel strategy to synthesize highly branched high-molecular-weight polyethylenes with controllable chain topologies ranging from linear to hyperbranched dendritic structure. In this work, we report the performance of this novel series of polyethylenes as lubricant viscosity-index improvers. By examining a range of such model polymers possessing various tailor-designed chain topologies, we report the first systematic study on the unique effects of chain topology on the polymers' viscosity thickening ability and shear stability. It is demonstrated that hyperbranched polyethylenes we prepared possess extremely high shear stability with almost zero shear degradation regardless of their high molecular weight. Our study shows that these hyperbranched polymers have great potential for formulating high-performance lubricants with superior properties.

The heterogeneous atom transfer radical polymerization of methyl methacrylate using the catalyst complex CuBr/1,1,4,7,10,10-hexamethyltriethylene tetramine (CuBr/HMTETA) was undertaken under a number of conditions to elucidate the effects of key process variables. It was found that a 100-fold reduction in metal salt concentration, to 21 ppm in solution (metal to intiator = 0.01:1), reduced polymerization rates 3-fold. PMMA produced at these low concentrations had high initiator efficiencies (Ieff = 88%) and low polydispersisties (1.1). Decreasing metal salt concentrations 1000-fold, to 2 ppm (Mt:I = 0.001:1), resulted in PMMA with controlled molecular weights (Ieff = 96%) but high polydispersities (2.1). Polymerization rates above and below a metal concentration of 210 ppm were found to be proportional to the metal salt concentration to the power of 0.05 and 0.37, respectively. Rates were found to increase with ligand concentration to the power of 0.52. Stirring was found to increase polymerization rates ...

Long-chain-branched isotactic polypropylenes (LCBed PP) were synthesized by copolymerizing propylene with a small amount of nonconjugated α,ω-diene (1,9-decadiene or 1,7-octadiene) using the catalyst system of rac-Me2Si(2-MeBenz[e]Ind) 2 ZrCl 2 (MBI)/MMAO. In this approach, the LCB structures were introduced by the incorporation of in situ generated macromonomers with pendant 1-octenyl or 1-hexenyl groups during the polymerization. A detailed study on the effects of diene concentration on polymer properties was conducted. Polymer chain microstructures were characterized by 13 C NMR, GPCV, and DSC. In the propylene/1,9-decadiene copolymerization, a series of LCBed polymer samples with the long-chain-branch density (LCBD) of up to 0.53 branch structures per 1000 carbons were produced with the diene concentrations of 0.177-3.54 mmol/L at 40 and 25 °C. A diene concentration of 35.4 mmol/L yielded cross-linked polymer gels. In the copolymerization of propylene and 1,7-octadiene, in addition to a small fraction of LCB structures produced, a cyclic seven-member ring structure was observed due to the cycloaddition of 1,7-octadiene. The cyclization significantly decreased the LCBD in the polymers. A small-amplitude oscillatory shear flow measurement was conducted to evaluate the rheological properties of the LCBed polymers. Compared to the linear samples prepared at the same polymerization conditions, the LCBed polymers exhibited enhanced low-frequency complex viscosity, improved shear-thinning, increased dynamic moduli, and reduced phase angle. The samples also showed thermorheological complexity and enhanced activation energy at low frequencies. These particular properties are related to the LCB in the polymers and become more significant with the increase of LCBD. The LCBed polypropylenes were also blended with their counterpart linear samples and demonstrated the improvement of rheological properties.

A high-pressure, high-temperature continuous stirred-tank reactor (CSTR) system having approximately an ideal residence time distribution (RTD) has been set up for the polymerization of olefins utilizing metallocene catalysts. Preliminary experiments of ethylene polymerized with the metallocene catalyst system zirconocene dichloride (Cp2ZrCl2)/modified-methylaluminoxane (MMAO)/trimethylaluminum (TMA) in toluene at 1500 psig have been carried out. The reactor system showed good control over temperature, pressure, and ethylene feed rate. The steady state was obtained after four mean residence times (4 τ's). With increasing Cp2ZrCl2 concentration, the molecular weight (MW) of polyethylene (PE) decreased and the catalyst activity (kg of PE/([ethylene]·g of catalyst)) increased. With increasing temperature between 140 and 200 °C, the MW of PE decreased and molecular weight distribution (MWD) polydispersity increased. PEs with weight-average molecular weight (Mw) 18 000−52 000 were obtained. The catalyst activi...

Chemical modification of isotactic polypropylene via a free-radical mechanism was studied using an on-line electron spin resonance spectrometer. Peroxides were used to provide primary radicals upon thermal decomposition at elevated temperatures for the generation of polymer backbone radicals. Four types of peroxides, tert-butyl perbenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne-3, and benzoyl peroxide, at various concentration levels were employed. The ESR measurement demonstrated that the modification was accomplished via a free-radical mechanism. Both radical generation and termination were clearly observed. Peroxide type, concentration, temperature, and reaction time were the major factors that affected the radical concentration profiles. The radical concentration variations were used to estimate the radical termination rate constants.