Synthesis of new 1‐decene‐based LLDPE resins and comparison with the corresponding 1‐octene‐ and 1‐hexene‐based LLDPE resins

This article extends the composition of linear low‐density polyethylene (LLDPE) resins to that containing 1‐decene comonomer units, and examines the effects of comonomer (type and concentration) to copolymerization and physical properties of LLDPE resins. CGC metallocene technology, under high temperature and high pressure (industrial reaction condition), was used to prepare three types of well‐defined LLDPE copolymers containing 1‐hexene, 1‐octene, and 1‐decene units. They show high molecular weight with narrow molecular weight and composition distributions, comparative catalyst activities, and similar comonomer effects. However, 1‐decene seems to exhibit significantly higher comonomer incorporation than 1‐hexene and 1‐octene, which may be associated with its high boiling point, maintaining liquid phase during the polymerization. The resulting LLDPE copolymers show a clear structure–property relationship. Melting temperature and crystallinity of the copolymer are governed by mole % of comonomer. The increase of branch density linearly decreases the LLDPE melting point and exponential reduction of its crystallinity. On the other hand, the density of the copolymer decreases with the increase of comonomer weight %, which shows a sharp linear relationship in the low comonomer content. The tensile properties of 1‐decene‐based LLDPE are very comparative with those of the commercial LLDPE resins with similar compositions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 639–649, 2007     

Spatially inhomogeneous crystallinity in heterogeneous ethylene‐α‐olefin copolymers

The crystallinity development in heterogeneous ethylene‐1‐butene copolymers is compared with that in ethylene copolymers, with more bulky 1‐heptene as a comonomer. The thermal transitions of the 1‐heptene based copolymers persistently occur at higher temperatures than of the corresponding 1‐butene copolymers. The earlier crystallization onset is reflected in thicker primary crystals, which in turn are associated with the presence of longer ethylene sequences because of the inaccessibility of 1‐heptene to sterically shielded catalytic sites. In addition, the 1‐heptene based copolymers are characterized by a higher degree of primary crystallinity, whereas the 1‐butene copolymers exhibit more prominent secondary crystallization. The 1‐butene based copolymers thus have a less heterogeneous chemical composition distribution. At high comonomer contents, the highly heterogeneous nature of the 1‐heptene copolymers is emphasized by a more pronounced presence of low crystalline spherulite inclusions accomplished by the liquid–liquid phase separation of dissimilar polymeric chains before crystallization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3000–3018, 2005     

Melting behavior of polyethylene/α‐olefin copolymers: Narrow composition distribution copolymers and fractions from Ziegler–Natta and single‐site catalyst products

The melting temperature and heat of fusion were measured for an extensive series of compositionally uniform copolymers of ethylene with butene‐1, hexene‐1, and octene‐1. Fractions and whole polymers that exhibited minimal interchain compositional heterogeneity were from commercial copolymers made with either Ziegler–Natta (ZN) or single‐site metallocene catalysts. The present results do not support recent claims that ZN and corresponding metallocene catalyst copolymers melt at significantly different temperatures, nor the implication that comonomer incorporation is “blocky” in ZN copolymers. In five of the six comonomer/catalyst systems the dependencies of the melting temperature on comonomer type and amount were scarcely distinguishable. This common behavior is the same as that for a model random copolymer, so we conclude that most ethylene/α‐olefin copolymers have random distributions of ethylene sequences. The exception in the present study is a metallocene ethylene/butene‐1 copolymer that melts at lower temperatures and apparently has perceptibly alternating sequence distributions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3416–3427, 2004     

Permeation measurements in ethylene‐1‐hexene,ethylene‐1‐octene,and ethylene‐1‐dodecene copolymers synthesized with metallocene catalysts

The permeation behavior of different ethylene‐1‐hexene, ethylene‐1‐octene, and ethylene‐1‐dodecene copolymers synthesized with metallocene catalysts has been analyzed. These copolymers cover a wide range of comonomer contents, so their crystallinities display rather considerable variations. The results for the permeability to oxygen of the different ethylene copolymers show that the main factor influencing the permeability is the noncrystalline fraction, although some influence of the kind of comonomer may also be present, which may be explained by the fact that when the alkyl branch of the α‐olefin is longer, there is an increase in the free volume in the amorphous and interfacial regions, causing slightly higher values of the permeability coefficient. From the results with different gases, it follows that, in general, an increase in the size of the penetrant (as expressed by its kinetic diameter or critical molar volume) leads to an increase in the solubility and a decrease in the diffusion coefficient. A wide range of permeability values is covered by these ethylene copolymers, depending basically on the crystallinity of the sample, but the permselectivity of CO₂ with respect to oxygen (and probably between other pairs of gases) does not differ very much among the different copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2174–2184, 2003     

Morphology of homogeneous copolymers of ethylene and 1‐octene. II. Structural changes on annealing

Based on DSC evidence, annealing of ethylene‐1‐octene copolymers results in a gradually increasing thermal stability of the original, metastable, crystals. SAXS and WAXD were used to monitor the structural changes involved after isothermal annealing for a fixed time at step‐wise higher temperatures. A series of samples that differ in molar mass and comonomer content, ranging from 0 to 11.8 mol % 1‐octene, were cooled at two extreme rates from 150°C, i.e., a quenching into liquid nitrogen and a controlled cooling at 0.1°C per minute to room temperature. The crystallinities of the quenched linear polyethylenes (LPEs), being included in this study as reference materials, and of the quenched copolymer with a 1‐octene content of 2.1 mol % are always found to be lower than the crystallinities of the slowly cooled samples. On the other hand, higher crystallinities can be found for the quenched copolymers with a higher comonomer content compared to the slowly cooled specimens. A sequence of cocrystallization and recrystallization events is proposed to explain this contraintuitive, but reproducible experimental fact. This reasoning can also account for the steeper increase of the amorphous layer thickness of the latter slowly cooled copolymers compared to the quenched samples. All copolymers show a very moderate increase of the lamellar thickness after each heating step. Besides additional crystallization and recrystallization, lateral growth of the crystals and an increase of the crystallite density can account for the gradual increase of the thermal stability of copolymer crystals during prolonged annealing. The morphological effects observed for the LPEs confirm earlier findings. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 83–100, 1999     

The copolymerization of propylene with higher,linear α‐olefins

Propylene was copolymerized with the linear α‐olefins 1‐octene, 1‐decene, 1‐tetradecene, and 1‐octadecene. The metallocene catalyst Me₂Si(2‐Me Benz[e]Ind)₂ZrCl₂, in conjunction with methylalumoxane as a cocatalyst, was used to synthesize the copolymers. The copolymers were characterized by ¹³C and ¹H NMR with a solvent mixture of 1,2,4‐trichlorobenzene (TCB) and benzene‐d₆ (9/1) at 100 °C. Thermal analyses were carried out to determine the melting and crystallization temperatures, whereas the molecular weights and molecular weight distributions were determined by gel permeation chromatography with TCB at 140 °C. Glass‐transition temperatures were determined with dynamic mechanical analysis. Relationships among the comonomer type and amount of incorporation and the melting/crystallization temperatures, glass‐transition temperature, crystallinity, and molecular weight were established. Moreover, up to 3.5% of the comonomer was incorporated, and there was a decrease in the molecular weight with increased comonomer content. Also, the melting and crystallization temperatures decreased as the comonomer content increased, but this relationship was independent of the comonomer type. In contrast, the values for the glass‐transition temperature also decreased with increased comonomer content, but the extent of the decrease was dependent on the comonomer type. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4110–4118, 2000     

Living copolymerization of ethylene/1‐octene with fluorinated FI‐Ti catalyst

Living copolymerization of ethylene and 1‐octene was carried out at room temperature using the fluorinated FI‐Ti catalyst system, bis[N‐(3‐methylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato] TiCl₂/dried methylaluminoxane, with various 1‐octene concentrations. The comonomer incorporation up to 32.7 mol % was achieved at the 1‐octene feeding ratio of 0.953. The living feature still retained at such a high comonomer level. The copolymer composition drifting was minor in this living copolymerization system despite of a batch process. It was found that the polymerization heterogeneity had a severe effect on the copolymerization kinetics, with the apparent reactivity ratios in slurry significantly different from those in solution. The reactivity ratios were nearly independent of polymerization temperature in the range of 0–35 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Co‐ and terpolymerization of ethylene,propylene, and higher α‐olefins with high propylene contents using metallocene catalysts

The copolymerization of propylene/ethylene and terpolymerization of propylene/ethylene/α‐olefins using long‐chain α‐olefins such as 1‐octene and 1‐decene have been carried out using EtInd₂ZrCl₂//methylaluminoxane. High concentrations of propylene and low concentrations of α‐olefins (near 2 mol % of the total olefin concentration in the liquid phase) were used. The effect of the ethylene concentration in copolymerizations of propylene/α‐olefins was studied at medium ethylene contents (12 and 40 mol % in the gas phase). The polymers were molecularly characterized by gel permeation chromatography‐multiangle laser light scattering, wide‐angle X‐ray scattering, Fourier transform infrared spectroscopy, and DSC analyses. The shorter α‐olefin studied (1‐octene) produced the highest improvement of activity in terpolymerization at 12 mol % ethylene in the gas phase. About 2 mol % of 1‐octene in the liquid phase increases the activity and decreases the molecular weight of terpolymers with respect to corresponding copolymers, whereas the mp is increased by almost 30 °C. The “termonomer effect” is less evident when higher amounts of ethylene are used. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1136–1148, 2001     

Differential scanning calorimetry,small‐angle X‐ray scattering,and wide‐angle X‐ray scattering on homogeneous and heterogeneous ethylene‐α‐copolymers

The objective of this work was to use both X‐ray and differential scanning calorimetry techniques in a comparative study of the lamellar and crystalline structures of heterogeneous and homogeneous ethylene‐α‐copolymers. The samples differed in the comonomer type (1‐butene, 1‐hexene, 1‐octene, and hexadecene), comonomer content, and catalyst used in the polymerizations. Step crystallizations were performed with differential scanning calorimetry, and the crystallinity and lamellar thicknesses of the different crystal populations were determined. Wide‐angle X‐ray scattering was used to determine crystallinities, average sizes of the crystallites, and dimensions of the orthorhombic unit cell. The average thickness, separation of the lamellae, and volume fractions of the crystalline phase were determined by small‐angle X‐ray scattering (SAXS). The results revealed that at densities below 900 kg/m³, polymers were organized as poorly organized crystal bundles. The lamellar distances were smaller and the lamellar thickness distributions were narrower for the homogeneous ethylene copolymers than for the heterogeneous ones. Step‐crystallization experiments by SAXS demonstrated that the long period increased after annealing. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1860–1875, 2001     

Copolymerization of propylene with various higher α‐olefins using silica‐supported rac‐Me2Si(Ind)2ZrCl2

The copolymerization of propylene with 1‐hexene, 1‐octene, 1‐decene, and 1‐dodecene was carried out with silica‐supported rac‐Me₂Si(Ind)₂ZrCl₂ as a catalyst. The copolymerization activities of the homogeneous and supported catalysts and the microstructures of the resulting copolymers were compared. The activity of the supported catalyst was only one‐half to one‐eighth of that of the homogeneous catalyst, depending on the comonomer type. The supported catalyst copolymerized more comonomer into the polymer chain than the homogeneous catalyst at the same monomer feed ratio. Data of reactivity ratios showed that the depression in the activity of propylene instead of an enhancement in the activity of olefinic comonomer was responsible for this phenomenon. We also found that copolymerization with α‐olefins and supporting the metallocene on a carrier improved the stereoregularity and regioregularity of the copolymers. The melting temperature of all the copolymers decreased linearly with growing comonomer content, regardless of the comonomer type and catalyst system. Low mobility of the propagation chain in the supported catalyst was suggested as the reason for the different polymerization behaviors of the supported catalyst with the homogeneous system. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3294–3303, 2001     

Classification of homogeneous copolymers of propylene and 1‐octene based on comonomer content

The solid‐state structure and properties of homogeneous copolymers of propylene and 1‐octene were examined. Based on the combined observations from melting behavior, dynamic mechanical response, morphology with primarily atomic force microscopy, X‐ray diffraction, and tensile deformation, a classification scheme with four distinct categories is proposed. The homopolymer constitutes Type IV. It is characterized by large α‐positive spherulites with thick lamellae, good lamellar organization, and considerable secondary crystallization. Copolymers with up to 5 mol % octene, with at least 28 wt % crystallinity, are classified as Type III. Like the homopolymer, these copolymers crystallize as α‐positive spherulites, however, they have smaller spherulites and thinner lamellae. Both Type IV and Type III materials exhibit thermoplastic behavior characterized by yielding with formation of a sharp neck, cold drawing, strong strain hardening, and small recovery. Copolymers classified as Type II have between 5 and 10 mol % octene with crystallinity in the range of 15–28%. Type II materials have smaller impinging spherulites and thinner lamellae than Type III copolymers. Moreover, the spherulites are α‐negative, meaning that they exhibit very little crystallographic branching. These copolymers also contain predominately α‐phase crystallinity. The materials in this category have plastomeric behavior. They form a diffuse neck upon yielding and exhibit some recovery. Type I copolymers have more than 10 mol % octene and less than 15% crystallinity. They exhibit a granular texture with the granules often assembled into beaded strings that resemble poorly developed lamellae. Type I copolymers crystallize predominantly in the mesophase. Materials belonging to this class deform with a very diffuse neck and also exhibit some recovery. They are identified as elastoplastomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4357–4370, 2004     

High molar mass ethene/1‐olefin copolymers synthesized with acenaphthyl substituted metallocene catalysts

The influence of ligand structure on copolymerization properties of metallocene catalysts was elucidated with three C₁‐symmetric methylalumoxane (MAO) activated zirconocene dichlorides, ethylene(1‐(7, 9)‐diphenylcyclopenta‐[a]‐acenaphthadienyl‐2‐phenyl‐2‐cyclopentadienyl)ZrCl₂ ( 1 ), ethylene(1‐(7, 9)‐diphenylcyclopenta‐[a]‐acenaphthadienyl‐2‐phenyl‐2‐fluorenyl)ZrCl₂ ( 2 ), and ethylene(1‐(9)‐fluorenyl‐(R)1‐phenyl‐2‐(1‐indenyl)ZrCl2 ( 3 ). Polyethenes produced with 1 /MAO had considerable, ca. 10% amount of trans‐vinylene end groups, resulting from the chain end isomerization prior to the chain termination. When ethene was copolymerized with 1‐hexene or 1‐hexadecene using 1 /MAO, molar mass of the copolymers varied from high to moderate (531–116 kg/mol) depending on the comonomer feed. At 50% comonomer feed, ethene/1‐olefin copolymers with high hexene or hexadecene content (around 10%) were achievable. In the series of catalysts, polyethenes with highest molar mass, up to 985 kg/mol, were obtained with sterically most crowded 2 /MAO, but the catalyst was only moderately active to copolymerize higher olefins. Catalyst 3 /MAO produced polyethenes with extremely small amounts of trans‐vinylene end groups and relatively low molar mass 1‐hexene copolymers (from 157 to 38 kg/mol) with similar comonomer content as 1 . These results indicate that the catalyst structure, which favors chain end isomerization, is also capable to produce high molar mass 1‐olefin copolymers with high comonomer content. In addition, an exceptionally strong synergetic effect of the comonomer on the polymerization activity was observed with catalyst 3 /MAO. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 373–382, 2008     

Differences between Ziegler–Natta and Single‐Site Linear Low‐Density Polyethylenes as Characterized by Inverse Gas Chromatography

Summary: Zero‐pressure weight‐fraction‐based Henry's constants of two alkanes, two alkenes, and benzene in Ziegler–Natta (ZN) and single‐site (ss) linear low‐density polyethylenes (LLDPE) with different average branch contents, molecular‐weight averages ( and ), and polydispersity indices (PDI) were measured in the temperature range of 170 to 230 °C using the technique of inverse gas chromatography. For both types of LLDPEs, the measured was insensitive to molecular weight and PDI. However, the branch content dependence differed significantly. In particular, ZN‐LLDPE exhibited a strong branch content dependence on while ss‐LLDPE did not. In fact, depending on the temperature and solvent used, of ZN‐LLDPE could drop as much as 21% with an increase in an average branch content from 13 to 35 branches per 1 000 backbone carbons, while the differences of between ss‐LLDPEs with comparable differences in branch content were well within experimental uncertainties (5%). This observation is also supported by the fact that comparable ZN‐ and ss‐LLDPEs exhibited larger differences in at higher average branch contents. The above findings strongly suggested that the liquid morphologies of ZN‐ and ss‐LLDPEs differ considerably. In particular, the local chain conformation and free volume characteristics (i.e., the size distribution and/or spatial distribution of the free volume holes) of them are rather different. Such differences become more pronounced at higher temperatures.

The weight‐fraction‐based Henry's constant of n‐hexane and hex‐1‐ene in Ziegler–Natta (ZN) and single‐site (ss) linear low‐density polyethylenes (LLDPE) with different average branch contents.     

Synthesis of highly thermostable norbornene‐isoprene‐1‐octene terpolymer with titanium catalyst

Terpolymerization of norbornene (NB), isoprene (IP), and 1‐octene was achieved by using fluorenylamido‐ligated titanium catalyst, which showed very high activity for the copolymerization of NB and various α‐olefins. The content of IP in the terpolymer was controlled by the feed ratio and reaction temperature up to 7 mol %. The incorporated IP was mainly inserted in 1,4‐addition. The polymer was dissolved into common solvents such as toluene and chloroform, which enabled the preparation of a transparent film by solution casting process. The degradation temperature of the terpolymer was comparable with other cyclic olefin copolymers and the glass transition temperature (T_g) was higher than that of NB‐1‐octene copolymer with almost the same NB content. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2136–2140     

Effect of chain blockiness on the phase behavior of ethylene‐octene copolymer blends

New challenges and opportunities for polyolefin blends arise from the recent introduction of olefin block copolymers (OBCs). In this study, the effect of chain blockiness on the miscibility and phase behavior of ethylene‐octene (EO) copolymer blends was studied. Binary blends of two statistical copolymers (EO/EO blends) that differed in comonomer content were compared with blends of an EO with a blocky EO copolymer (EO/OBC blends). The blends were rapidly quenched to retain the phase morphology in the melt and the phase volumes were obtained by atomic force microscopy (AFM). Two EOs of molecular weight about 100 kg/mol were miscible if the difference in octene content was less than about 10 mol % and immiscible if the octene content difference was greater than about 13 mol %. The blocky nature of the OBCs reduced the miscibility and broadened the partial miscibility window of the EO/OBC blends compared with the EO/EO blends. The EO/OBC blends were miscible if the octene content difference was less than 7 mol % and immiscible above 13 mol % octene content difference. It was also found that the phase behavior of EO/OBC blends strongly depended on blend composition even for constituent polymers of about the same molecular weight. Significantly more demixing was observed in an OBC‐rich blend (EO/OBC 30/70 v/v) than in an OBC‐poor blend (EO/OBC 70/30 v/v). An interpretation based on extractable fractions of the OBC described the major features of the EO/OBC (30/70 v/v) blends. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1554–1572, 2009     

Synthesis,characterization, and ethylene (Co)polymerization behavior of trichlorotitanium 2‐(1‐(arylimino)propyl)quinolin‐8‐olates

A series of trichlorotitanium complexes containing 2‐(1‐(arylimino)propyl)quinolin‐8‐olates was synthesized by stoichiometric reaction of titanium tetrachloride with the corresponding potassium 2‐(1‐(arylimino)propyl)quinolin‐8‐olates and was fully characterized by elemental analysis, nuclear magnetic resonance spectroscopy, and by single‐crystal X‐ray diffraction study of representative complexes. All titanium complexes, when activated with methylaluminoxane, exhibited high catalytic activity toward ethylene polymerization [up to 1.15 × 10⁶ g mol^?1(Ti) h^?1] and ethylene/α‐olefin copolymerization [up to 1.54 × 10⁶ g mol^?1 (Ti) h^?1]. The incorporation of comonomer was confirmed to amount up to 2.82 mol % of 1‐hexene or 1.94 mol % of 1‐octene, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Metallocenic copolymers of ethylene and 5,7‐dimethylocta‐1,6‐diene: Structural characterization and mechanical behavior

The relationship between the structure and mechanical properties has been established for several copolymers of ethylene and 5,7‐dimethylocta‐1,6‐diene synthesized with a metallocene catalyst. A dependence on the composition and polymerization temperature has been found. The branches cannot be incorporated into the orthorhombic crystal lattice, and consequently, structural parameters such as the crystallinity and crystal size are considerably affected as the 5,7‐dimethylocta‐1,6‐diene content increases in the copolymers. The viscoelastic relaxations have been analyzed and compared with those exhibited by high‐density polyethylene (HDPE). The β relaxation does not appear in HDPE and is exclusively seen in the copolymers. As the 5,7‐dimethylocta‐1,6‐diene content rises, the intensity of this process is increased, and its location is shifted to a lower temperature up to comonomer contents of approximately 6–8 mol % in the copolymers. On the other hand, the α mechanism associated with motion within the crystalline regions is also moved to a lower temperature and its intensity is diminished as the 5,7‐dimethylocta‐1,6‐diene molar fraction increases in the copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3797–3808, 2004     

Controlled copolymerization of 1‐octene and butyl methacrylate via RAFT and their nonisothermal model‐free thermokinetic decomposition study

Reversible addition fragmentation chain transfer (RAFT) copolymerization of 1‐octene and butyl methacrylate (BMA) was carried out for the first time using 4‐cyano‐4‐(phenylcarbonothioylthio)pentanoic acid as RAFT agent in N,N′‐dimethyl formamide. Poly(1‐octene‐co‐BMA) copolymers with well‐controlled molecular weights and narrow molecular weight distribution were obtained throughout the polymerization. The copolymers have been well characterized by different analytical techniques such as SEC, FT‐IR, NMR, SEM, AFM, XRD, and TG analyses. FT‐IR and NMR analyses confirmed the synthesis of poly(1‐octene‐co‐BMA) copolymers. SEM and AFM analyses demonstrated the wavy‐lamellar morphological structure of the copolymers. Thermogravimetric analysis revealed good thermal stability of poly(1‐octene‐co‐BMA) copolymers synthesized via RAFT mediated polymerization. The thermokinetic parameters were evaluated by adopting model‐free methods of Friedman and Flynn–Wall–Ozawa using the nonisothermal thermogravimetric data. The multivariate nonlinear regression analysis established the most appropriate kinetic model and the corresponding kinetic parameters of thermal decomposition of poly(1‐octene‐co‐BMA) copolymers were also calculated. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2093–2103     

Characterization of homogeneous ethylene/1‐octene copolymers made with a single‐site catalyst. CRYSTAF analysis and calibration

The crystallizability of narrow composition, homogeneous ethylene/1‐octene copolymers made with a constrained geometry catalyst, measured by CRYSTAF, follows a straight line correlation with the amount of total comonomer incorporated. The potential use of these resins as standards to calibrate CRYSTAF and TREF techniques is discussed. Although most of the resins analyzed have a narrow chemical composition distribution, there seems to be a relation between the broadness of the distribution and molecular weight, as predicted by Stockmayer's bivariate distribution. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 89–93, 1999     

Radical polymerization of 1‐alkenes catalyzed by lithium salts of carboranes

Radical polymerization of selected 1‐alkenes, (1‐hexene, 1‐octene and 2‐methyl‐1‐heptene), initiated with classical radical initiators and catalyzed by lithium salts of selected carboranes was studied. In accordance with recently published results it was found that the use of radical initiators under catalysis by “naked” lithium cation of carboranes promotes the radical polymerization of 1‐alkenes, otherwise nonpolymerizable by the radical mechanism. However, although in our experiments relatively high monomers conversions are reached for some of the thermal initiators used, only low‐molecular‐weight oligomers with M_n < 1000 are formed, regardless of the initiator and carborane anion used. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011