Functional Polyolefins Research Articles

Polyolefins/Poly(3‐hydroxybutyrate‐co‐hydroxyvalerate) blends compatibilization: Morphology, rheological, and mechanical properties

AbstractPolypropylene/poly(3‐hydroxybutyrate‐co‐hydroxyvalerate) blend (PHBV) and polyethylene/PHBV blend were prepared by twin screw extruder using preformed copolymer (EVOH‐g‐PHBV) as compatibilizer or with functional polyolefins that can react in situ with the PHBV phase to form POs‐g‐PHBV. Scanning electron microscopy shows that by using either EVOH‐g‐PHBV preformed copolymer or formed copolymers in situ both emulsify the phase interface and reduce the interfacial tension, which result in an enhancement on the mechanical properties of compatibilized blends. Enhancement is more or less pronounced depending on the used PO matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Control of Charge-Carrier Mobility via In-Chain Spacer Length Variation in Sequenced Triarylamine Functionalized Polyolefins.

A set of six perfectly regioregular pendant 2,7-bis(phenyl-m-toluylamino)fluorene (TPF) functionalized polyolefins for use as charge transporting materials in polymer light emitting diodes (PLEDs) were prepared and characterized. Synthesis of these materials is straightforward, requiring only three or four steps, depending on the polymer, and final isolated yields over all steps combined were greater than 40% in all but one case. Most notably, these materials exhibit charge-carrier mobilities that can be controlled over 3 orders of magnitude by variation of the number of intermediary carbons (spacer length) between the pendant TPF groups. The range of hole mobilities encompasses the electron mobilities of common electron transport materials/emitters such as Alq3 and PBD, thus, affording the opportunity to fabricate electroactive polyolefin based PLEDs with well matched charge-carrier mobilities and improved performance. We believe this approach to charge-carrier mobility control in electroactive materials could be easily extended to other aryl systems with different HOMO-LUMO levels for energy level and mobility matching with various emitters.

Melting of polymernanocrystals: a comparison between experiments and simulation

Polymer nanocrystals have attracted considerable attention because of their potential applications in future technology and their fascinating properties which differ from those of corresponding bulk materials. The essential influence of the nanointerface in nanocrystals is apparent in the linear dependence of the melting temperature with the inverse sheet thickness, i.e. the Gibbs–Thomson behaviour. Yet, few experimental and theoretical works have been attempted to highlight the influence of nanointerfaces on the thermal properties of nanocrystals. In this work, simulations were used to evaluate the melting temperature of crystalline polymer nanosheets. Ensuing results were compared favourably to experimental melting temperatures stemming from alkane chains and functional polyolefins, thus validating our simulation approach. Both experimental and simulated results followed Gibbs–Thomson behaviour and a procedure was devised to extract the heat of melting as well as the surface energy from these results. Thus, surface energy of various nanocrystals was found to be widely different for various experimental systems, demonstrating the significance of the environment on thermal properties of nanocrystals.

Synthesis of Functional Polyolefins using Metallocenes: A Comprehensive Review

The copolymerization mainly of ethylene and propylene with various polar functional comonomers, using various metallocenes and the methylaluminoxane (MAO) cocatalyst, has been primarily reviewed from the perspective of the following two subjects. One is the influence of the various functional groups on the copolymerization reactions, and the properties of the resulting products; the other is the areas of future research. The functional groups have been classified into oxygen-, nitrogen-, and halogen-containing moieties; borane-containing α-olefins; silanes; dienes; cyclic olefins; as well as styrene and its various derivatives. The following areas—synthesis of easily soluble functional cooligomer/copolymer; products with uniform distribution of the comonomer; establishment of relation among the catalyst structure and the various steps of copolymerization (initiation, propagation, and chain termination); the degradation and stabilization study of the functional copolymers and the correlation of the same with the catalyst structure; the application of supported metallocenes to synthesize the resulting polymer; the minimization of multi-step synthesis; and the development MAO cocatalyst formulation (to improve the activity and comonomer incorporation)—have been identified to be the subjects of future research, which will be of special importance to the researchers working in functional polyolefins.

New Approaches in Precise Synthesis of Polyolefins Containing Polar Functionalities by Olefin Copolymerizations Using Transition Metal Catalysts

Recent successful examples for synthesis of new polyolefins containing polar functionalities by adopting the approaches by (a) direct copolymerization of olefin with polar monomer using living radical or coordination insertion methods, (b) direct alkane C-H activation/functionalization (post functionalization of polyolefins), and by (c) controlled incorporation of reactive functionalities (and the subsequent introduction of polar funtionalities under mild conditions) by coordination polymerization in the presence of transition metal complex catalysts have been described. In particular, our recent efforts for precise synthesis of polyolefins containing polar functionalities by (i) efficient incorporation of reactive functionality by copolymerization of ethylene with nonconjugated diene using nonbridged half-titanocene catalysts and (ii) subsequent chemical modifications under mild conditions have been introduced.

Recent Progress in Precise Synthesis of Polyolefins Containing Polar Functionalities by Transition Metal Catalysis

Recent successful examples for synthesis of new polyolefins containing polar functionalities by transition metal complex catalysis have been reviewed. The contents are consisted of the following sections: 1) background, 2) radical copolymerization, 3) direct alkane activation/functionalization (post functionalization of polyolefins), 4) controlled incorporation of reactive functionalities (and the subsequent introduction of polar funtionalities under mild conditions) by coordination polymerization. In particular, we wish to introduce our recent approach for synthesis of polyolefins containing polar functionalities via copolymerization of ethylene with nonconjugated diene using nonbridged half-titanocenes. Keywords: Polyolefin, olefin polymerization, ATRP, C-H activation, homogeneous catalysis

ChemInform Abstract: Versatile Pathways for in situ Polyolefin Functionalization with Heteroatoms: Catalytic Chain Transfer

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Nanocomposites based on polyolefins and functional thermoplastic materials

AbstractPolyolefins are today the most used thermoplastic materials thanks to the high technology and sustainability of the polymerization process, their excellent thermomechanical properties and their good environmental compatibility, including easy recycling. In the last few decades much effort has been devoted worldwide to extend the applications of polyolefins by conferring on them new properties through mixing and blending with different materials. In this latter context, nanocomposites have recently offered new exciting possibilities. This has been made possible on the basis of the improvement of polyolefin functionalization processes with the availability of several olefin homo‐ and copolymers bearing a small (generally less than 1 mol%) amount of backbone grafted polar groups. These are indeed adequate to endow favourable interface interactions with polar macromolecules and inorganic compounds, leading first to compatible blends and then to microcomposites. The successful use of nanostructured dispersed materials has opened, on a similar basis, the way to nanocomposites as described in this review. This review provides a broad and updated description of the synthetic routes to nanostructured biphase materials having the typical structural properties of polyolefins (continuous matrix) but showing enhanced thermomechanical properties, thermostability, lower flammability, lower gas permeability and electrical and optical properties, thanks to the presence of an extended interphase interaction with very different nanodispersed species. Copyright © 2008 Society of Chemical Industry

Versatile Pathways for In Situ Polyolefin Functionalization with Heteroatoms: Catalytic Chain Transfer

Chain-transfer processes represent highly effective chemical means to achieve selective, in situ d- and f-block-metal catalyzed functionalization of polyolefins. A diverse variety of electron-poor and electron-rich chain-transfer agents, including silanes, boranes, alanes, phosphines, and amines, effect efficient chain termination with concomitant carbon-heteroelement bond formation during single-site olefin-polymerization processes. High polymerization activities, control of polyolefin molecular weight and microstructure, and selective chain functionalization are all possible, with distinctly different mechanisms operative for the electron-poor and electron-rich reagents. A variety of metal centers (early transition metals, lanthanides, late transition metals) and single-site ancillary ligand arrays (metallocene, half-metallocene, non-metallocene) are able to mediate these selective chain-termination/functionalization processes.

Synthesis and characterisation of novel functional polyolefin containing sulfonic acid groups

The strong polar group, sulfonic acid, has successfully been introduced into ethylene/allylbenzene copolymers without degradation or crosslinking via chlorosulfonation reaction with chlorosulfonic acid as a chlorosulfonating agent in 1,1,2,2-tetrachloroethane followed by hydrolysis. The degree of sulfonation (DS) can be easily controlled by changing the ratio of chlorosulfonic acid to the pendant phenyls of the copolymer. The microstructure of sulfonated copolymers were unambiguously revealed by 1H NMR and 1H– 1H COSY spectral analyses, which indicates that all the sulfonation reactions exclusively took place at the para-position of the aromatic rings. The thermal behaviors were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC data exhibit a systematic trend of melting temperature increasing with DS. TGA data of sulfonated copolymers show an increase in degradation temperature from 444 to 460 °C compared to the received copolymer. Sulfonated copolymers also show an additional minor loss of mass at approximately 261 °C, which is not observed in the received copolymer. The wetting properties of the sulfonated copolymers were also evaluated by contact angle measurement, and a notable increase in surface hydrophilicity was identified.

Polypropylene/polysulfone compatibilized blends

AbstractPolypropylene and polysulfone have not been previously blended because of viscosity and processing temperature differences. These blends, which showed structure‐property improvements with the addition of functional polyolefins, were made into environmentally friendly membranes. J. VINYL ADDIT. TECHNOL., 13:143–146, 2007. © 2007 Society of Plastics Engineers

Synthesis of Chain‐End Functionalized Polyolefins with a Bis(phenoxy imine) Titanium Catalyst

AbstractPolyethylenes and highly syndiotactic poly(propylene)s possessing chain end hydroxyl groups were synthesized by living polymerizations using L2TiCl2 [1, L: C6F5NCH(2OC6H33tBu)]/MAO and functionalized α‐olefins, H2CCH(CH2)nY [2; YOAlMe2, n = 4 (2a); YOSiMe3, n = 9 (2b)]. Because the primary insertion of 2 to a cationic species L2Ti+Me (3) derived from 1/MAO is much faster than the successive secondary insertion of 2, addition of an equimolar amount of 2 to 3 resulted in the quantitative formation of L2Ti+CH2CH(Me)(CH2)nY [4; YOAlMe2, n = 4 (4a); YOSiMe3, n = 9 (4b)]. These cationic species 4 served as functionalized initiators for the living polymerization of both ethylene and propylene and afforded polyolefins having extremely narrow molecular weight distributions and a hydroxyl group at the initiating chain end. The terminating chain end of the syndiotactic poly(propylene)s was also functionalized by adding an excess amount of 2b as a chain end capping agent to the living L2Ti–polymeryl species. Due to much slower insertion of the second molecule of 2b relative to the first one, the obtained polymers were end capped quantitatively by a single molecule of 2b. Telechelic syndiotactic poly(propylene)s were successfully synthesized through a living polymerization initiated by 4b and an end capping using 2b.magnified image

Synthesis of novel functional polyolefin containing carboxylic acid via Friedel–Crafts acylation reaction

The strong polar group, carboxylic acid, has triumphantly been introduced into ethylene and allylbenzene copolymers without obvious degradation or crosslinking via Friedel–Crafts (F–C) acylation reaction with glutaric anhydride (GA), succinic anhydride (SA) and phthalic anhydride (PA) in the presence of anhydrous aluminum chloride in carbon disulfide. Some important reaction parameters were examined in order to optimize the acylation process. In the optimum reaction conditions, almost all of the phenyls can be acylated with any anhydride. The microstructure of acylated copolymer was characterized by FT-IR, 1H NMR and 1H– 1H COSY. All the peaks of acylated copolymers can be accurately attributed, which indicates that all the acylation reactions occur only at the para-positions of the substituent of the aromatic rings. The thermal behavior was studied by differential scanning calorimetry (DSC), showing that the melting temperatures ( T ms) of acylated copolymers with GA firstly decrease slowly and then increase significantly with the increase of the amount of carboxyl acid groups.

Copolymerization of Ethylene and 10‐Undecen‐1‐ol using a Montmorillonite‐Intercalated Metallocene Catalyst: Synthesis of Polyethylene/Montmorillonite Nanocomposites with Enhanced Structural Stability

AbstractSummary: Ethylene and 10‐undecen‐1‐ol have been successfully copolymerized by an organically modified montmorillonite (OMMT)‐intercalated metallocene catalyst, Et[Ind]2ZrCl2, activated by methylaluminoxane (MAO). The obtained hydroxy‐functionalized polyethylene (PE‐OH)/OMMT nanocomposites exhibit enhanced structural stability as compared with the neat PE‐based ones, with no significant collapse of the nanocomposite structure being detected by WAXD examination after high‐temperature processing. The simultaneous polyolefin functionalization provides an effective and convenient solution to stabilize the PE/MMT nanocomposite structure formed by in‐situ polymerization. magnified image

Sequenced Ethylene−Propylene Copolymers: Effects of Short Ethylene Run Lengths

Two sequenced ethylene−propylene (EP) copolymers possessing methyl groups every fifth (EP5) or seventh (EP7) carbon have been prepared using an olefin metathesis polycondensation/hydrogenation strategy, thus generating methyl branched polyolefins with short ethylene run lengths of 4 or 6 carbons, respectively. Precise spacing of methyl branches along both copolymer backbones imparts pristine microstructure and targeted comonomer ratios in the copolymer. Extensive NMR spectral data are presented detailing polymer microstructure, branching analysis, and end-group identification. Thermal analysis using differential scanning calorimetry revealed multiple low-temperature relaxations for EP7 and glass transition temperature of −63 °C for EP5, and FT-IR analysis suggests no crystallinity under ambient conditions. A new ADMET monomer synthesis is also reported for the development of highly functionalized polyolefins or sequenced ethylene copolymers.

Design and synthesis of structurally well-defined functional polypropylenes via transition metal-mediated olefin polymerization chemistry

Functionalization of polyolefins is an industrially important yet scientifically challenging research subject. This paper summarizes our recent effort to access structurally well-defined functional polypropylenes via transition metal-mediated olefin polymerization. In one approach, polypropylenes containing side chain functional groups of controlled concentrations were obtained by Ziegler-Natta-catalyzed copolymerization of propylene in combination with either living anionic or controlled radical polymerization of polar monomers. The copolymerization of propylene with 1,4-divinylbenzene using an isospecific MgCl2-supported TiCl4 catalyst yielded polypropylenes containing pendant styrene moieties. Both metalation reaction with n-butyllithium and hydrochlorination reaction with dry hydrogen chloride selectively and quantitatively occurred at the pendant reactive sites, generating polymeric benzyllithium and 1-chloroethylbenzene species. These species initiated living anionic polymerization of styrene (S) and atom transfer radical polymerization (in the presence of CuCl and pentamethyldiethylenetriamine) of methyl methacrylate (MMA), respectively, resulting in functional polypropylene graft copolymers (PP-g-PS and PP-g-PMMA) with controllable graft lengths. In another approach, chain end-functionalized polypropylenes containing a terminal OH-group with controlled molecular weights were directly prepared by propylene polymerization with a metallocene catalyst through a selective aluminum chain transfer reaction. Both approaches proved to be desirable polyolefin functionalization routes in terms of efficiency and polymer structure controllability.

Functionalization of polyolefins with maleic anhydride in melt state through ultrasonic initiation

The functionalization reaction of high-density polyethylene (HDPE), linearly low-density polyethylene (LLDPE), polypropylene (PP) and EPDM rubber with maleic anhydride (MAH) in melt state through ultrasonic initiation was studied. The effect of ultrasonic intensity on the percentage of grafting, viscosity–average molecular weight, melt flow rate and gel content of the functionalized products were investigated by means of chemical titration, Fourier-transform infra-red spectroscopy (FT-IR), intrinsic viscosity and melt flow rate, etc. The molecular structures of the functionalized products prepared via ultrasonic initiation and via peroxide initiation were characterized by 1H NMR spectroscopy. The results show that the functionalization reaction of HDPE, LLDPE and EPDM with MAH can be realized by ultrasonic initiation. This reaction mainly consists of the chain scission under ultrasonic irradiation, the end chain reaction of the produced macroradicals with MAH, and the terminated reaction of the produced succinyl radicals with the macroradicals or H* radicals through recombination or dismutation. The functionalized product through ultrasonic initiation mainly consists of the products containing an anhydride ring attached to the chain terminus. And the products prepared through peroxide initiation mainly contain an anhydride ring grafted on the side chain.

New Functional Polyolefins: Towards a Bridge Between Catalytic and RAFT Polymerizations?

AbstractSummary: Di‐polyethylenyl magnesium compounds, obtained by a transition metal catalyzed chain growth reaction on butyloctyl magnesium, are reacted with a range of disulfides of thiocarbonylated compounds (RC(S)SSC(S)R). Xanthate, dithiocarbamate, dithioester, and trithiocarbonate‐functionalized polyethylenes are thus obtained and characterized by 1H NMR and IR spectroscopy, and MALDI TOF mass spectrometry. These macroRAFT agents may serve as building blocks for the synthesis of block copolymers based on polyolefins and polar segments.Thio thiocarbonylate‐terminated polyethylene chains are easily prepared in high yield by a two step reaction and analyzed by MALDI‐TOF mass spectrometry.imageThio thiocarbonylate‐terminated polyethylene chains are easily prepared in high yield by a two step reaction and analyzed by MALDI‐TOF mass spectrometry.

Terminal Functionalization of Polypropylene by Radical-Mediated Thiol−Ene Addition

The radical-mediated addition of alkanethiols to the terminal unsaturation of polypropylene (PP) is used to prepare functional polyolefin derivatives without altering the molecular weight of the parent material. The sulfide product of thiol−ene addition, as well as the internal olefin resulting from a remarkable thiyl radical-mediated olefin migration, is characterized using a model hydrocarbon, 2,4-dimethylhept-1-ene. The yield of 3-mercaptopropyltrimethoxysilane (MPTMS) addition to atactic-PP is examined in detail, and the functionalization of high molecular weight isotactic-PP is used to produce moisture-curing resins that bind to siliceous fillers. The limited unsaturation content of PP, along with the high temperatures needed to modify the resin in its melt state, is shown to impact negatively on the reaction conversion due to the reversibility of thiyl radical attack on olefin.

Controlled, Copper-Catalyzed Functionalization of Polyolefins

Laboratorio de Catalisis Homogenea, Departamento de Quimica y Ciencia de los Materiales, Unidad Asociada al CSIC, Campus de El Carmen s/n, Universidad de Huelva, 21007-Huelva, Spain; Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716; Department of Chemistry, University of North Carolina, Chapel Hill, CB3290, Chapel Hill, North Carolina 27599; and Universitat Konstanz, Fachbereich Chemie, 78457 Konstanz, Germany