Saturated Polymers Research Articles

Controlled Ethylene Polymerization Catalyzed by Cp$\rm{{_{2}^{\ast}}}$ZrBu2/[Ph3C] [B(C6F5)4]/iBu4Al2O above Room Temperature

AbstractThe ternary system composed of Cp$\rm{{_{2}^{\ast}}}$ZrBu2 (Cp*=Me5Cp), [CPh3][B(C6F5)4], and tetraisobutyldialuminoxane (TIBAO) catalyzed the polymerization of ethylene in a controlled fashion at temperatures up to 60 °C. The consumption of ethylene remained constant during the polymerization process, the molecular weight of the polyethylene increased linearly with time, and polydispersity indexes down to 1.3 were obtained. Characterization of the polyethylene by 13C‐NMR and FT‐IR spectroscopy did not indicate any branching or CC linkages, even for polymer produced at 40 °C or above. The linear and saturated polymer structure is due to the absence of β‐hydride transfer, β‐hydride elimination and chain walking during the polymerization. The absence of termination reactions is consistent with the system's demonstrated controlled polymerization.

The effect of adsorption kinetics on film formation of silica/PVA suspension

Particle/binder/solvent systems are widely used in many applications and have long been studied. Understanding and controlling polymer adsorption in these complex material systems are important to achieve successful final performance. In this study, the effect of polymer adsorption on film formation and the relation between the microstructures of the suspension and film have been investigated by measuring the amount of polymer adsorption and the stress development during drying. In terms of mixing (or dispersion) time ( t m ), the adsorption amount ( Γ PVA), characteristic stress ( σ ch ) and dried film density ( ρ) showed a similar behavior in the form of 1 - e t m / τ with a single characteristic time τ = 45 h, which implies that the drying process is determined by this single time constant. The porous and non-uniform microstructure of the dried film at short t m became close-packed and uniform with longer t m . The polymer adsorption was found to play a key role in film formation as it introduces steric repulsion in suspension and suppresses the flocculation during solvent evaporation. It was also pointed out that enough mixing time for the saturated polymer adsorption is critical to acquire the consolidated and uniform film microstructure.

C1 polymerisation and related C–C bond forming ‘carbeneinsertion’ reactions

In this critical review we summarise the currently available 'C1 polymerisation' techniques as valuable alternatives for 'C2 polymerisation' in the preparation of saturated main-chain carbon-based polymers. C1 polymerisation involves the growth of polymers from monomers delivering only one functionalised carbon unit (C1 monomers; typically 'carbene precursors') in each chain-growth step, which contrasts with common polymerisation of C=C bond containing substrates (C2 monomers). In the general introduction (section 1) we comment on the availability of C1 monomers and the most important differences between C1 and C2 polymerisation techniques, highlighting the opportunities provided by C1 polymerisation to prepare new polymer structures. In section 2 we describe several Lewis acid mediated C1 polymerisation reactions based on diazocompounds and sulfur ylides as C1 monomers. Some of these are 'living polymerisation' reactions which allow the synthesis of functional telechelic block-copolymers and polymethylenic homo-polymers with a wide variety of different functional end-groups at both polymer chain-ends in a controlled fashion. Miscellaneous related reactions of other C1 monomers are described in section 3. Transition metal mediated C1 polymerisation methods in section 4 allow the polymerisation of polar functionalised C1 monomers. Several homogeneous and heterogeneous catalysts are capable of producing polymers from a variety of diazo compounds, some of which even allow the formation of stereoregular polar functionalised polymers (which is a major challenge in traditional olefin polymerisation). An overview of the current state-of-the art, challenges and opportunities, as well as an overview of the available mechanistic information (sections 4 and 5) is provided. Some related C-C bond forming reactions proceeding via (migratory) carbene insertion (section 6) are also discussed (106 references).

Polymers from Functional Macrolactones as Potential Biomaterials: Enzymatic Ring Opening Polymerization, Biodegradation, and Biocompatibility

We systematically investigated a series of polymers derived from macrolactones, namely, pentadecalactone, hexadecalactone, and their unsaturated analogues ambrettolide and globalide as potential biomaterials. By enzymatic ring-opening polymerization these monomers can conveniently be polymerized to high molecular weight. The polymers are highly crystalline with melting points around 95 degrees C for the saturated polymers and lower melting points for the unsaturated polymers (46-55 degrees C). All polymers are nontoxic as measured by an MTT assay for metabolic cell activity of a 3T3 mouse fibroblast cell line. Degradation studies showed no hydrolytic or enzymatic degradability of the polymers, which was ascribed to the high crystallinity and hydrophobicity of the materials. The unsaturated polymers were cross-linked in the melt, yielding fully amorphous transparent materials with a gel content of 97%.

Polymer functionalization by free radical addition to alkynes

AbstractA new chemical modification of saturated polymers involving free radical addition to mono‐substituted alkynes is presented and examined in terms of reaction yield, graft structure, and changes to molecular weight. Solvent‐free, peroxide‐initiated reactions of ethyl propiolate and poly(ethylene oxide) provide good yields of ethyl (2‐E,Z)‐3‐alkylacrylates, whereas less efficient hydrogen atom donation by polyethylene impacts negatively on reaction yields and encourages alkyne oligomerization. Model compounds are used to characterize alkyne grafting products, and to probe the relationship between reagent properties, reaction yields, and product structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7386–7394, 2008

Feasibility of density functional methods to predict dielectric properties of polymers

Feasibility of density functional theory (DFT) to predict dielectric properties such as polarizability of saturated polymers is investigated. Small saturated molecules, methane and propane, which is a monomer of polypropylene chain, are used in testing the methods. Results for polarizabilities based on several density functionals together with different basis sets are compared and contrasted with each other, with results by Hartree-Fock and second-order Moller-Plesset perturbation theory, as well as experimental data. The generalized gradient approximation PW91 method together with the 6-311++G(**) basis set is found to be the most suitable method, in terms of sufficient accuracy and computational efficiency, to calculate polarizabilities for large oligomers of polypropylene. The dielectric constant is then determined using the calculated polarizabilities and the Clausius-Mossotti equation. The molecular DFT methods at the PW916-311++G(**) level together with the Clausius-Mossotti equation give dielectric constants for saturated polymers such as polypropylene in good accordance with the experimental values.

Efficient Red-Emitting Electrophosphorescent Polymers

We report the synthesis and characterization of a series of electrophosphorescent polymers with a polyfluorene backbone, containing a red-emitting iridium complex and carrier-transporting units as the substitutes of the C-9 position of fluorene. Different specimens and contents of the hole-transporting moieties were found to influence the electroluminescent properties of the polymers. Incorporation of a hole-transporting/electron-blocking interfacial layer and utilization of an efficient electron injection cathode led to the saturated red-emitting electrophosphorescent polymer devices with the peak luminance efficiency and power conversion efficiency of 9.3 cd A−1 and 10.5 lm W−1, respectively. The efficiencies were 8 cd A−1/8 lm W−1 and 5.9 cd A−1/4.6 lm W−1, respectively, at 100 and 1000 cd m−2.

Synthesis of polymeric antioxidants based on ring-opening metathesis polymerization (ROMP) and their antioxidant ability for preventing polypropylene (PP) from thermal oxidation degradation

Norbornene derivatives 1– 5 bearing hindered phenol groups were synthesized and undergone ring-opening metathesis polymerization (ROMP) with Grubbs 1st generation catalyst to prepare the corresponding polymeric antioxidants. After hydrogenation with p-toluenesulfonylhydrazide (TSH), polymeric antioxidants with saturated polymer chain were prepared. The resulting polymeric antioxidants were characterized by gel permeation chromatography (GPC), 1H NMR and differential scanning calorimetry (DSC). As to polymerization activity, monomer 1 had the highest ROMP activity, while monomer 5 could not undergo homopolymerization due to the steric hindrance. The antioxidant ability of these polymeric antioxidants which was determined by oxidation induction temperature (OIT) in polypropylene (PP) system is to protect PP against thermal oxidation. Results showed that the OIT of PP increased obviously when PP was stabilized by the adding of polymeric antioxidants.

Rubber Vulcanizates Degradation and Stabilization

Abstract Degradation of rubber vulcanizates in the presence and absence of air as well as in presence of ozone is reviewed in this paper. The paper also outlines the means to overcome this undesirable phenomenon. Under anaerobic aging conditions, which is termed as reversion, the vulcanizates are exposed to elevated temperature in the absence of oxygen. The consequence of this process is reflected in a decline in physical properties and performance characteristics. These changes are directly related to modifications of the original crosslink structure. Decomposition reactions tend to predominate and thus leading to a reduction in crosslink density and physical properties as observed during extended cure or when using higher curing temperatures. The decrease in network density is common when vulcanizates are subject to an anaerobic aging process. However, in the presence of oxygen, the network density is increased with the main chain modifications playing a vital role. Over the years the rubber industry has developed several compounding approaches to address the changes in crosslink structure during thermal aging. This paper gives a review of these compounding approaches. As with many formulation changes in rubber compounding, there is a compromise that must be made when attempting to improve one performance characteristic. For example, improving the thermal stability of vulcanized natural rubber compounds by reducing the sulfur content of the crosslink through the use of the more efficient vulcanization systems will reduce dynamic performance properties such as fatigue resistance. The challenge is to define a way to improve thermal stability while maintaining dynamic performance characteristics. In the second part, the protection against aerobic ageing as well as in ozone environment is reviewed. The anti-degradant effects are summarized and means to counteract are outlined. The most commonly used antidegradants are N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD) and N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD). Although conventional antidegradants such as IPPD and 6PPD are still the most widely used antidegradants in rubber, there is a trend and demand for longer-lasting and non-staining products. The relatively low molecular weight (MW) antioxidants have undergone an evolutionary change towards higher molecular weight products with the objective to achieve permanence in the rubber polymer, without loss of antioxidant activity. In the last two decades, several approaches have been evaluated in order to achieve this objective: attachment of hydrocarbon chains to conventional antioxidants in order to increase the MW and compatibility with the rubber matrix; oligomeric or polymeric antioxidants; and polymer bound or covulcanizable antioxidants. The disadvantage of polymer bound antioxidants was tackled by grafting antioxidants onto low MW polysiloxanes, which are compatible with many polymers. New developments on antiozonants have focused on non-staining and slow migrating products, which last longer in rubber compounds. Several new types of non-staining antiozonants have been developed, but none of them appeared to be as efficient as the chemically substituted p-phenylenediamines. The most prevalent approach to achieve non-staining ozone protection of rubber compounds is to use an inherently ozone-resistant, saturated backbone polymer in blends with a diene rubber. The disadvantage of this approach however, is the complicated mixing procedure needed to ensure that the required small polymer domain size is obtained

Stability study of saturated red polymer light-emitting diodes

Saturated red polymer light-emitting diodes have been fabricated with a single emitting polymer blend layer of poly[2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEH-PPV) and poly[9,9-dioctylfluorene-co-4,7-di-2-thienyl-2,1,3-benzothiadiazole] (PFO-DBT15). Saturated red emission with the Commission Internationale de l’Eclairage (CIE) coordinates of (0.67, 0.33) was obtained. The device stability was investigated. The results showed that energy transfer occurred from MEH-PPV to PFO-DBT15, and MEH-PPV improved the hole injection and transportation.

Highly efficient saturated red electrophosphorescence from isoquinoline-based iridium complex containing triphenylamino units in polymer light-emitting devices

To obtain highly efficient saturated red-emitting polymer light-emitting devices, the opto-physical and electrophosphorescent properties of a novel isoquinoline-based iridium complex containing triphenylamino units were investigated. The devices using this iridium complex as a dopant and a blend of poly(9,9-dioctylfluorene) and 2- tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole as a host matrix displayed bright saturated red emission at 637 nm with Commission Internationale de I’Eclairage coordinate of (0.64, 0.31). The maximum external quantum efficiency of 10.8% photos/electron and current efficiency of 4.6 cd/A at 1.7 mA/cm 2, and the peak brightness of 5453 cd/m 2 at 228 mA/cm 2 were obtained in the device at 2% dopant concentration.

Hybrid organic–inorganic assemblies built up from saturated heteropolyoxoanions and copper coordination polymers with mixed 4,4′-bipyridine and 2,2′-bipyridine ligands

Three new organic–inorganic hybrid compounds [Cu I(2,2′-bipy)(4,4′-bipy) 0.5] 2[Cu I(2,2′-bipy)(4,4′-Hbipy)][Cu I(4,4′-bipy)] 2[P 2W 18O 62] · 3H 2O ( 1), [Cu I(2,2′-bipy)(4,4′-bipy) 0.5] 2[Cu I(4,4′-bipy)] 2[PW 12O 40] · 0.25H 2O ( 2), and[Cu I(4,4′-bipy)] 3[PMo 12O 40] · en · 3H 2O ( 3) (2,2′- bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine), have been hydrothermally synthesized. Compound 1 represents the first 1D ladderlike structure formed by Dawson-type polyoxoanion [P 2W 18O 62] 6− and coordination polymer with mixed 4,4′-bipy and 2,2′-bipy ligands. The novel structure of 2 is composed of 1D hybrid zigzag chains linked by { Cu ( 4 , 4 ′ -bipy ) } n n + chains into a 3D framework. In compound 3, the [PMo 12O 40] 3− clusters are hung on { Cu ( 4 , 4 ′ -bipy ) } n n + chains to form a new 1D chain.

Utilization of water/alcohol-soluble polyelectrolyte as an electron injection layer for fabrication of high-efficiency multilayer saturated red-phosphorescence polymer light-emitting diodes by solution processing

Highly efficient multilayer red polymer light-emitting diodes were fabricated by solution process-ing from iridium complex, bis(1-(3-(9,9-dimethyl-fluorene-2-yl)phenyl)isoquinoline-C2,N′) iridium(III)acetylacetonate, doped into polyfluorene as a host and with a water/alcohol-soluble polymer, poly[(9,9-bis(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene)-4,7-(2,1,3-benzoselenadiazole)]dibromide (PFN) as electron injection layer. The device with the structure ITO∕PEDOT-PSS(50nm)∕PVK(40nm)∕PFO:PBD:Ir(DMFPQ)2acac(2%,75nm)∕PFN(20nm)∕Ba(4.5nm)∕Al(150nm) showed an external quantum efficiency of 18.0% and luminance efficiency of 9.8Cd∕A at a current density of 1.1mA∕cm2, a peak emission at λmax=636nm, and Commission International de I’Eclairage coordinates of (0.665, 0.319). The efficiency remained as high as QE=11.1%, and LE=6.0cd∕A, at a current density of 100mA∕cm2, and a luminance of 6140cd∕m2.

A bicyclic conjugated diene monomer, tetrahydroindene, for cationic polymerization and a novel alicyclic hydrocarbon polymer with heat resistance

AbstractThis study was directed toward the cationic polymerization of tetrahydroindene (i.e., bicyclo[4.3.0]‐2,9‐nonadiene), a bicyclic conjugated diene monomer, with a series of Lewis acids, especially focusing on the synthesis of high‐molecular‐weight polymers and subsequent hydrogenation for novel cycloolefin polymers with high service temperatures. EtAlCl2 or SnCl4 induced an efficient and quantitative cationic polymerization of tetrahydroindene to afford polymers with relatively high molecular weights (number‐average molecular weight > 20,000) and 1,4‐enchainment bicyclic main‐chain structures. The subsequent hydrogenation of the obtained poly(tetrahydroindene) with p‐toluenesulfonyl hydrazide resulted in a saturated alicyclic hydrocarbon polymer with a relatively high glass transition (glass‐transition temperature = 220 °C) and improved pyrolysis temperature (10% weight loss at 480 °C). The new diene monomer was randomly copolymerized with cyclopentadiene at various feed ratios in the presence of EtAlCl2 to give novel cycloolefin copolymers, which were subsequently hydrogenated into alicyclic copolymers with variable glass‐transition temperatures (70–220 °C). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6214–6225, 2006

Suppression of Energy‐Transfer Between Conjugated Polymers in a Ternary Blend Identified Using Scanning Near‐Field Optical Microscopy

Scanning near-field optical microscopy (see figure) has been employed to study energy transfer within a ternary blend of the conjugated polymers poly(9,9-dioctylfluorene) (F8), poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT), and the saturated polymer poly(methyl methacrylate) (PMMA). Although the morphology of such phase-separated blends resembles that of simple binary systems composed of a saturated and a unsaturated polymer, it was found that energy transfer between F8 and F8BT is significantly hindered by the diluting effect of the PMMA.

Achieving saturated red photoluminescence and electroluminescence with readily synthesized maleimide-arylamine copolymers

Maleimide-based red fluorescent copolymers were easily synthesized from palladium catalyzed polycondensation of N-alkyl-3,4-bis(4-bromophenyl)maleimide with commercially available or readily prepared secondary aryldiamines. The copolymers were characterized by gel permeation chromatography, differential scanning calorimetry, cyclic voltammetry, UV–vis absorption, and fluorescence spectroscopy. They showed brilliant red fluorescence in solution (toluene) with emission maximum in the range of 617–638 nm, although severely red-shifted in thin films. With judicious selection of aryldiamine monomers, the red-shifting of the thin film fluorescence can be largely diminished. The structure and property (molecular weight, glass transition temperature, and fluorescence) relationships were analyzed and deciphered as well. A light-emitting device has been fabricated with maleimide-arylamine copolymer in demonstrating the potentials for saturated red polymer light-emitting diodes (PLEDs).

Use of electron accelerators in polymer composite material production technology

Problems of accelerating crosslinking reactions of saturated and unsaturated polymers and mixtures were solved in the work on creation of electron-chemical technology; highly effective modifying systems were found which allow reducing the optimum absorbed doses of radiation by 3–4 times and obtaining polymer composites with high physicomechanical properties. The effect of the target ingredients on the electron-chemical processes that take place in polymer composites was investigated; the possibility of regulating the process, performance, and special properties of the composites to formulate optimum formulas for polymer composite materials with the required characteristics was demonstrated. Methods of electron-chemical covulcanization of blends of polymers of different chemical natures with a valuable set of properties which cannot be covulcanized by traditional thermochemical or radiation effects were demonstrated. A calculation was performed and the selection of electron accelerators for use in the man-made leather industry was substantiated.

Formation of TiO 2–polymer composite microparticles by rapid expansion of CO 2 saturated polymer suspensions with high shear mixing

A method is reported for the preparation of highly loaded TiO 2–polymer composite particles by rapid expansion of carbon dioxide (CO 2) saturated polymer suspensions with high shear mixing. Suspensions of CO 2 saturated polymer solution and TiO 2 nanoparticles were agitated in high-pressure vessel equipped with a column agitator and mechanical seals. The rotation speed and peripheral velocity were set at 5000 rpm and 40.8 m/s, respectively. The polymers were poly(lactic acid) (PLA; M.W. = 10,000) and poly(styrene)- b-(poly(methyl methacrylate)- co-poly(glycidyl methacrylate)) copolymer (PS- b-PMMA- co-PGMA, M.W. = 5000). After agitation and rapid expansion of the CO 2 saturated polymer suspensions to an aqueous phase, polymer microspheres were obtained and very small on the order of only micrometers. The structure and morphology of the microspheres were investigated by SEM, TEM, XRD and turbidity measurement. The polymer microspheres obtained were highly loaded TiO 2–polymer composites. According to TEM photograph of the cross section of polymer particle, loading ratio of TiO 2 in polymer particles is 52%. The TiO 2 content in the polymer particles was increased by an increase in the rotational speed of the agitator, and consequently the shear stress in the high-pressure vessel. The shear stress between the column agitator and the inside wall accelerates the dispersion of TiO 2 nanoparticles in CO 2 saturated polymer suspensions. On the other hand, agglomerated TiO 2 nanoparticles were observed on the surface of polymer microparticles produced by rapid expansion of mixtures with conventional mixing, and the loading ratio of TiO 2 in the polymer matrix was very low. The loading ratio of TiO 2 in the polymer particle was very low and less than 1%.

Periodic and High-Temperature Disordered Conformations of Polytetrafluoroethylene Chains: An ab Initio Modeling

We report here the main results of a successful attempt to predict some macroscopic properties of representative polymers of technological relevance both in regular and disordered forms by using first principle quantum mechanical approaches at microscopic level. Until now, the prediction of the structural and thermal properties of those polymers has been mostly a domain of molecular mechanics methods. To overcome the limits of those classical computational tools whenever physical properties are significantly influenced by stereoelectronic effects (e.g., electron rich substituents), we employed methods rooted in the Density Functional Theory (DFT). A general computational strategy including the proper choice of periodic boundary conditions (PBC), functional, basis set, and model system size, has been tested and validated for saturated polymers such as polyethylene and isotactic/syndiotactic polypropylenes. On the basis of these results, a comprehensive study of poly(tetrafluoroethylene) (PTFE) chains in both regular periodic and disordered conformations has been performed. A statistical approach has been next applied to obtain the thermal concentration of defects and to reproduce the thermal behavior of the investigated polymer. At the end, a very good agreement with experimental X-ray diffraction and IR results has been achieved, definitely reaching a good understanding of the widely studied disorder phenomenon determining the main technological properties of poly(tetrafluoroethylene) (the trade Teflon) and, at the same time, identifying the proper computational tools to investigate perfluoro-compounds and other complex polymeric systems.

Formation of elastomeric network polymers from ambient heterogeneous hydrosilations of carboranylenesiloxane and branched siloxane monomers

AbstractThe Karstedt catalyst‐catalyzed ambient‐condition hydrosilation reactions in hexane of a monomeric vinyl‐containing carboranylenesiloxane, 1, and three‐branched siloxane crosslinker monomers were discovered to produce elastomeric network polymers at very rapid rates of formation. The flexible and transparent films of the saturated elastomeric network polymers were observed to possess low glass‐transition temperatures (below −35 °C). Similar hydrosilation reactions at two different reactant ratios involving a diethynyl‐containing carboranylenesiloxane, 2, and the siloxane crosslinkers produced partially hydrosilated and completely hydrosilated polymeric networked systems, which were transparent and elastomeric at room temperature. The glass‐transition temperatures of all the polymeric systems formulated from 2 were below 0 °C. The elastomeric polymeric networks from 1 and 2 were found to have degradation temperatures in the range of 500–550 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 147–155, 2006