In this work, high melt flow rate (MFR) polypropylene (HF-PP) and polypropylene/poly(ethylene-co-propylene) in-reactor alloys (HF-PP/EPR) with MFR ≈ 30 g/10 min were synthesized by spherical MgCl2-supported Ziegler–Natta catalyst with cyclohexylmethyldimethoxysilane (CHMDMS) or dicyclopentyldimethoxysilane (DCPDMS) as external donor (De). The effects of De on polymerization activity, chain structure, mechanical properties, and phase morphology of HF-PP and HF-PP/EPR were studied. Adding CHMDMS caused more sensitive change of the polymers MFR with H2 than DCPDMS, and produced PP/EPR alloys containing more random ethylene-propylene copolymer (r-EP) and segmented ethylene-propylene copolymer (s-EP). CHMDMS also caused formation of s-EP with higher level of blockiness than DCPDMS. HF-PP/EPR alloy prepared in the presence of DCPDMS exhibited higher flexural properties but lower impact strength than that prepared with CHMDMS. Toughening efficiency of the rubber phase was nearly the same in the alloys prepared using CHMDMS or DCPDMS as De, but stiffness of the alloy can be improved by using DCPDMS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42984.
It is highly desirable to develop novel n-type organic small molecules as an efficient electron-transport layer (ETL) for the replacement of PCBM to obtain high-performance metal-oxide-free, solution-processed inverted perovskite solar cells (PSCs) because this type of solar cells with a low-temperature and solution-based process would make their fabrication more feasible and practical. In this research, the new azaacene QCAPZ has been synthesized and employed as non-fullerene ETL material for inverted PSCs through a solution-based process without the need for additional dopants or additives. The as-fabricated inverted PSCs show a power conversion efficiency up to 10.26 %. Our results clearly suggest that larger azaacenes could be promising electron-transport materials to achieve high-performance solution-processed inverted PSCs.
In this article, comonomer effects in copolymerization of ethylene and 1-hexene with four MgCl2-supported Ziegler-Natta catalysts using either ethylene or 1-hexene as the main monomer were investigated. It was found that no matter which monomer was used as the main monomer, the polymerization activity was significantly enhanced by introducing small amount of comonomer. In copolymerization with ethylene as the main monomer, the strength of comonomer effects was much stronger in active centers producing low-molecular-weight polymer than those producing high-molecular-weight polymer. In copolymerization with 1-hexene as the main monomer, the number of active centers ([C*]/[Ti]) was determined, and the propagation rate constants (kp) were calculated. Deconvolution of the polymer molecular weight distribution into Flory components were made to study the active center distribution. Introduction of small amount of ethylene caused marked increase in the number of active centers and decrease in average chain propagation rate constant. Introducing internal electron donor in the catalyst enhanced not only the number of active centers but also the chain propagation rate constant. In copolymerization of 1-hexene with small amount of ethylene, the internal donor weakened the comonomer effects to some extent and changed the distribution of comonomer effects among different types of active centers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41264.
The influence of combined external donor (ED) (diphenyldimethoxysilane/dicyclopentyldimethoxysilane) and combined cocatalyst (triethylaluminum/triisobutylaluminum) on propylene polymerization with MgCl2-supported Ziegler–Natta catalyst in the presence of hydrogen was investigated. By deconvolution analysis of the molecular weight distribution (MWD) into multiple Flory components, the influence of ED and cocatalyst on the active center distribution of the catalyst was demonstrated, and the mechanism was discussed. Using combined cocatalyst and combined donor, iPP with high molecular weight, high isotacticity index, and broad MWD can be obtained. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41689.
Polyethylene-b-poly (ethylene glycol) (PE-b-PEG) was successfully synthesized by a coupling reaction of hydroxyl-terminated polyethylene (PE-OH) and isocyanate-terminated poly (ethylene glycol) (PEG-NCO). PE-OH was prepared by coordination chain transfer polymerization (CCTP) using 2,6-bis[1-(2,6-diisopropylphenyl)imino ethyl] pyridine iron (II) dichloride /dry ethylaluminoxane (DEAO) /diethyl zinc (ZnEt2) as catalyst and subsequent in situ oxidation with oxygen. The active centers of this catalyst system were counted, indicating that the active centers were more stable using DEAO as cocatalyst than using dry methylaluminoxane (DMAO) as cocatalyst. PEG-NCO was synthesized through the condensation reaction of monomethylpoly(ethylene glycol) (PEG) with isophoronediisocyanate (IPDI). Subsequently, the thermal characterization, morphological characterization and the application of these diblock copolymers was investigated. The results indicated that the diblock copolymers were effective compatilizers for polyethylene/poly(ethylene glycol) blends. Meanwhile, they were excellent surface modification agents for polyethylene membrane and glass sheet, it can efficiently turn a hydrophobic surface into a hydrophilic surface, or vice versa. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42236.
In this work, a series of polypropylene/poly(ethylene-co-propylene) (iPP/EPR) in-reactor alloys were prepared by MgCl2/TiCl4/diester type Ziegler-Natta catalyst with triethylaluminium/triisobutylaluminium (TEA/TIBA) mixture as cocatalyst. The influence of cocatalyst and external electron donor, e.g., diphenyldimethoxysilane (DDS) or dicyclopentyldimethoxysilane (D-donor), on the structure and mechanical properties of iPP/EPR in-reactor alloys were studied and discussed. According to the characterization results, PP/EPR was mainly composed of random poly(ethylene-co-propylene), segmented poly(ethylene-co-propylene), and high isotactic PP. Using TEA/TIBA mixture as cocatalyst and DDS as external electron donor, as TEA/TIBA ratio increased, the impact strength of iPP/EPR in-reactor alloys had an increasing trend. Using TEA/TIBA mixture as cocatalyst and D-donor as external electron donor, the impact strength of iPP/EPR in-reactor alloy were dramatically improved. In this case, the iPP/EPR in-reactor alloy prepared at TEA: TIBA = 4 : 1 was the toughest. The influence of cocatalyst and external electron donor on the flexural modulus and flexural strength could be ignored. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
In this article, a series of amphiphilic graft copolymers, namely poly(higher α-olefin-co-para-methylstyrene)-graft-poly(ethylene glycol), and poly(higher α-olefin-co-acrylic acid)-graft-poly(ethylene glycol) was used as modifying agent to increase the wettability of the surface of linear low-density polyethylene (LLDPE) film. The wettability of the surface of LLDPE film could be increased effectively by spin coating of the amphiphilic graft copolymers onto the surface of LLDPE film. The higher the content of poly(ethylene glycol) (PEG) segments, the lower the water contact angle was. The water contact angle of modified LLDPE films was reduced as low as 25°. However, the adhesion between the amphiphilic graft copolymer and LLDPE film was poor. To solve this problem, the modified LLDPE films coated by the amphiphilic graft copolymers were annealed at 110° for 12 h. During the period of annealing, heating made polymer chain move and rearrange quickly. When the film was cooled down, the alkyl group of higher α-olefin units and LLDPE began to entangle and crystallize. Driven by crystallization, the PEG segments rearranged and enriched in the interface between the amphiphilic graft copolymer and air. By this surface modification method, the amphiphilic graft copolymer was fixed on the surface of LLDPE film. And the water contact angle was further reduced as low as 14.8°. The experimental results of this article demonstrate the potential pathway to provide an effective and durable anti-fog LLDPE film. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
In this article, 1-octene and styrene was copolymerized by the supported catalyst (TiCl4/ID/MgCl2). Subsequently, by sulfonation reaction, sulfonated poly(1-octene-co-styrene)s which were amphiphilic copolymers were prepared. The copolymerization behavior between 1-octene and styrene is moderate ideal behavior. Copolymers prepared by this catalyst contain appreciable amounts of both 1-octene and styrene. Increase in the feed ratio of styrene/1-octene leads to increase in styrene content in copolymer and decrease in molecular weight. As the polymerization temperature increases, the styrene content in the copolymers increases, however, the molecular weight decreases. Hydrogen is an efficient regulator to lower the molecular weights of poly(1-octene-co-styrene)s. The sulfonation degree of the sulfonated poly(1-octene-co-styrene)s increased as the styrene content in copolymer increased or the molecular weight decreased. Thirty-six hour is long enough for sulfonation reaction. The sulfonated poly(1-octene-co-styrene)s can be used as effective and durable modifying agent to improve the wettability of polyethylene film and have potential application in emulsified fuels and for the stabilization of dispersions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Two new kinds of amphiphilic copolymers were synthesized in this work. Poly(1-octene-co-acrylic acid) copolymers were prepared through the copolymerization of 1-octene and tert-butyl acrylate, and the hydrolysis of tert-butyl acrylate units. Poly(1-octene-co-acrylic acid)-g-poly (ethylene glycol) copolymers were obtained from the esterification reaction between poly(1-octene-co-acrylic acid) and poly(ethylene glycol) monomethyl ether. They were characterized by means of 1H-NMR, 13C-NMR, GPC, and FTIR. These amphiphilic copolymers can form stable micelles in aqueous solutions. The critical micelle concentration was determined by fluorescence spectroscopy. The micellar morphology and size distribution were investigated by transmission electron microscopy and dynamic light scattering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
A series of polypropylene-graft-polystyrene (PP-g-PS) were prepared by solid-state graft polymerization of styrene (St) in the presence of tert-butyl perbenzoate (TBPB) and 2,2,6,6-tetramethyl-piperidinyloxy (TEMPO) using nascent spherical isotactic polypropylene (PP) granules as matrix. Reaction conditions such as ratio of TEMPO to TBPB, amount of TBPB and St, reaction time and temperature were investigated. The grafting degree (GD) decreased slightly with the addition of TEMPO, but the introduction of TEMPO reduced gel formation and degradation of PP chain. Introduction of camphor sulfonic acid in the TEMPO-mediated grafting polymerization system lead to evident increase in molecular weight of PP-g-PS and decrease of gel formation with slight changes of GD. GPC curves of the product synthesized with TEMPO addition showed obvious tailing at high molecular weight end. Complex viscosity in dependence on angular frequency of the melt of product showed obvious shear-thinning behaviors. All the experimental results indicated existence of long-chain branches in the product of graft polymerization. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The main place of solid-state graft polymerization in polypropylene (PP) granules has been believed to be the amorphous region of PP. In this work, the solid-phase morphology of nascent spherical PP (N-PP) granules was found to be markedly changed by an annealing treatment. The crystallinity of PP granules was almost doubled after annealing at 150°C for 12 h, whereas the porosity of the granules was unchanged. Solid-state grafting polymerizations of styrene initiated by tert-butyl perbenzoate in both N-PP and annealed polypropylene (A-PP) granules were compared under different reaction conditions. The formation of gel in the product could be completely depressed at a low concentration of the initiator when A-PP granules were used as the matrix and graft-polymerized at 120°C. Both the introduction of styrene and the annealing treatment of the PP granules led to a depression of polymer degradation in the process of the grafting reaction. However, using A-PP as the matrix caused an increase in the grafting degree at a relatively high concentration of the initiator. A reduction in the amorphous phase in the PP granules was thought to be the main reason for the effects of the annealing treatment on the structure of the graft polymerization products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Graft copolymers of polystyrene (PSt) with spherical polypropylene (PP) granules were synthesized by solid-state reaction. In the copolymerization as a by-product some gel was formed. The effects of the amount of free radical initiator, feed ratio of St monomer, species of free radical initiator, and composition of the spherical polyolefin granules on the grafting degree of PSt and the gelation were studied. It is found that larger amount of initiator used, and higher feed ratio of St monomer lead to a higher grafting degree and higher content of gel. During the cross-link reaction process, both styrene and free-radical participate in the reaction that discloses the reason of the increment of gel with the increment of styrene consumption or initiator consumption. Using PPR, which is a random copolymer of 95.1 mol % propylene units and 4.9 mol % ethylene units, as grafting matrix, higher grafting degree and higher content of gel can be reached than that using isotactic PP as grafting matrix. Using tert-butyl peroxy benzoate (TBPB) as initiator, under the same conditions there were more PSt grafted to the spherical PP granules and more gel formed than that using benzoyl peroxide (BPO) as initiator. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3682–3687, 2007
A spherical TiCl4/MgCl2-based catalyst was used in the synthesis of polyethylene/polypropylene/poly (ethylene-co-propylene) in-reactor alloys by sequential homopolymerization of ethylene, homopolymerization of propylene, and copolymerization of ethylene and propylene in gas-phase. Different conditions in the third stage, such as the pressure of ethylene–propylene mixture and the feed ratio of ethylene, were investigated, and their influences on the compositions, structural distribution and properties of the in-reactor alloys were studied. Increasing the feed ratio of ethylene is favorable for forming random ethylene–propylene copolymer and segmented ethylene–propylene copolymer, however, slightly influences the formation of ethylene-b-propylene block copolymer and homopolyethylene. Raising the pressure of ethylene–propylene mixture results in the increment of segmented ethylene–propylene copolymer, ethylene-b-propylene block copolymer, and PE fractions, but exerts a slight influence on both the random copolymer and PP fractions. The impact strength of PE/PP/EPR in-reactor alloys can be markedly improved by increasing the feed ratio of ethylene in the ethylene–propylene mixture or increasing the pressure of ethylene–propylene mixture. However, the flexural modulus decreases as the feed ratio of ethylene in the ethylene–propylene mixture or the pressure of ethylene–propylene mixture increases. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2481–2487, 2006
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