Carl-Eric Wilén

Synthesis of novel-dl-α-tocopherol-based and sterically-hindered-phenol-based monomers and their utilization in copolymerizations over metallocene/mao catalyst systems. A strategy to remove concerns about additive compatibility and migration

In this paper we present an initial study on various synthetic routes to novel polymerizable dl-α-tocopherol derivatives and to a styrenic sterically hindered phenol which was stimulated by our desire to conduct copolymerization with these monomers with α-olefins over different metallocene/methylalumoxane (MAO) catalyst systems. The syntheses of 6-hydroxyl-2,5,7,8-tetramethyl-2-(but-3-enyl)chroman (1) and 5,7,8-trimethyl-3-(hex-5-enyl)benzofuran-6-ol (2) were achieved by cyclocondensation of trimethylhydroquinone (TMHQ) with 3-methylhept-1,6-dien-3-ol and 2,7-octadienol, respectively. However, the latter tocopherol compound (2) could only be obtained in low yields, and all our attempts to isolate the product from its ring-opened isomers failed. This can be attributed to the fact that the reaction between TMHQ and 2,7-octadienol gave rise to a highly complex reaction mixture. Compound 3, 6-hydroxyl-2,2,8,9-tetramethyl-6-allylchroman, was prepared from the corresponding allylchromanoxy ether via Claisen rea...

Reaction of epoxy resin and hyperbranched polyacids

The condensation reaction between two different epoxy resins and a hyperbranched polyester (MAHP) [poly(allyloxy maleic acid-co-maleic anhydride)] was studied. We compared two kinds of diglycidyl ether bisphenol A type of epoxy resins with different molecular weights, that is, epoxy resin GY240 (M = 365 g/mol) and GT6064 (M = 1540 g/mol) in this reaction. The results showed a marked difference in their reaction pattern in terms of ability to form crosslinked polymer networks with MAHP. For the former low-molecular-weight epoxy resin, no crosslinking could be observed in good solvents such as THF or dioxane within the set of reaction conditions used in this study. Instead, polymers with epoxide functional degrees between 0.34 and 0.5 were formed. By contrast, the latter high-molecular-weight epoxy resin, GT6064, rapidly produced highly crosslinked materials with MAHP under the same reaction conditions. The spherical-shape model of hyperbranched polymer was applied to explain this difference in reaction behavior. Hence, we have postulated that low-molecular-weight epoxy resins such as GY240 are unable to crosslink the comparatively much bigger spherically shaped MAHP molecules. However, using high-molecular-weight epoxy resins greatly enhances the probability of crosslinking in this system. Computer simulations verified the spherical shape and condensed bond density of MAHP in good solvents, and submicron particle analysis showed that the average MAHP particle size was 9 nm in THF. Furthermore, the epoxy-functionalized polyesters were characterized by 1H NMR and FTIR, and the molecular weights and molecular-weight distributions were determined by size-exclusion chromatography.

rac-[Ethylenebis(2-(thexyldimethylsiloxy)indenyl)]zirconium dichloride: Synthesis, molecular structure and olefin polymerization catalysis

Abstract The synthesis and molecular structure of rac -[ethylenebis(2-(thexyldimethylsiloxy)indenyl)]zirconium dichloride ( 4 ), is reported. In combination with methylaluminoxane (MAO), 4 forms an active catalyst system for homogeneous polymerization of ethylene and propylene. The high activity of 4 /MAO is retained at low [Al]:[Zr] ratios [(150–250):1]. Decreasing polymerization temperature or the [Al]:[Zr] ratio results in production of polyethylene having a high molecular weight shoulder in its molecular weight distribution (MWD). Deconvolution of the MWDs into a series of calculated Flory-distribution curves indicates that with this catalyst system ethylene is polymerized by three different types of active sites, whereas propylene is predominantly polymerized by two active sites. Complex 4 crystallizes in the indenyl-backward conformation. The ligand backbone adopts the expected C 2 symmetry.

Hyperbranched polymers with maleic functional groups as radical crosslinkers

The crosslinking performance of the unsaturated hyperbranched polyester poly(allyloxy maleic acid-co-maleic anhydride) (MAHP) was investigated with copolymerizations of three different monomers: styrene, vinyl acetate, and methyl methacrylate. Both styrene and vinyl acetate afforded interpenetrating-polymer-network copolymer gels. The gels exhibited crosslink density gradients through the polymer matrices on a macroscopic level, and density maximums were concentrated around the MAHP moieties. The heterogeneity of the gels is briefly discussed in terms of a modified two-phase model, where one phase consists of an elastic part of low crosslinking density and the other phase consists of an inelastic dendritic part with a highly condensed bond density. Unlike the two-phase model developed by Choquet and Rietsch, the modified two-phase model takes into account that both phases swell in good solvents. Unlike copolymerizations employing styrene or vinyl acetate, the copolymerization of MAHP with methyl methacrylate afforded noncrosslinked starbranched copolymers that consisted of a MAHP core from which long poly(methyl methacrylate) branches were protruding. The different behaviors of the copolymerizations of the three monomers used in this study can rationally be explained by their different reactivity ratios with maleic end groups of MAHP.

Copolymerization of propylene and 4-(ω-alkenyl)-2,6-di-t-butylphenol over a supported high-activity Ziegler-Natta catalyst

Abstract Copolymerizations of propylene and 4-(ω-alkenyl)-2,6-di-t-butylphenol were performed at 70°C over a high-activity supported TiCl 4 MgCl 2 Ziegler-Natta catalyst, using Al(C 2 H 5 ) 3 as cocatalyst and diphenyldimethoxysilane as external electron donor. The 4-(ω-alkenyl)-2,6-di-t-butylphenol was pretreated with a stoichiometric molar amount of triethylaluminium prior to copolymerization. After the copolymerization the protecting group was removed by converting the phenol aluminium compound to OH functionality by HCl/ethanol treatment. The copolymerizability of 4-(ω-alkenyl)-2,6-di-t-butylphenol as a function of the number of methylene group spacers between the double bond and the phenol moiety was determined for four different spacers. The results show that the copolymerization yield as well as the phenol content of the produced copolymer increased with an increase of spacer chain length. The produced copolymers exhibited good thermo-oxidative stabilities also after a prolonged extraction with n-heptane.

Synthesis and molecular structure of rac-methylenebis(4,5,6,7-tetrahydro-1-indenyl) titanium dichloride

Abstract The reaction of indenylpotassium with 0.5 equiv. of chloromethylpivalate yields bis(3-indenyl)methane (1). Double deprotonation of 1 with two equiv of BuLi, reaction with TiCl4·2THF and subsequent hydrogenation yields rac-methylenebis(4,5,6,7-tetrahydro-1-indenyl) titanium dichloride (3) in 16% overall yield. The molecular structure of (3) reveals a very small acute angle of 98.9(2)° at the methylene bridge carbon atom.

Environmentally Friendly Transistors and Circuits on Paper

We created environmentally friendly low-voltage, ion-modulated transistors (IMTs) that can be fabricated successfully on a paper substrate. A range of ionic liquids (ILs) based on choline chloride (ChoCl) were used as the electrolytic layer in the IMTs. Different organic compounds were mixed with ChoCl to create solution-processable deep eutectic mixtures that are liquid or semiliquid at room temperature. In the final, solid version of the IMT, the ILs are also solidified by using a commercial binder to create printable transistor structures The semiconductor layer in the IMT is also substituted with a blend of the original semiconductor and a biodegradable polymer insulator. This reduces the amount of expensive and potentially harmful semiconductor used, and it also provides increased transistor performance, especially increasing the device switching speed. These environmentally friendly IMTs are then used to create ring oscillators, logic gates, and memories on paper.

Radiation stability of in situ stabilized polypropylene

Abstract The radiation stability upon exposure to high-energy radiation of different bi- and terpolymers such as poly[propylene- co -4-(hept-6-enyl)-2,6-di-tert-butylphenol], poly(propylene- co -6-phenylhex-1-ene) and poly[propylene- co -4-(hept-6-enyl)-2,6-di-tert-butylphenol- co -4-(hex-5- enyl)-2,2,6,6-tetramethylpiperidine] was studied. The films were exposed to a radiation dose of 25 kGy. The extent of radiation-induced degradation of the samples was determined by size exclusion chromatography. The most stable polymers found were a copolymer containing 0.82 wt% of 4-(hept-6-enyl)-2,6-di-tert-butylphenol and a commercial radiation-resistant polypropylene. The copolymers containing chemically bound hindered phenol moieties exhibited better protective properties than polypropylene reference samples containing the same concentration of admixed 3-(3,5-di-tert-butyl-4-hydroxylphenyl)propionate (Irganox 1010). The copolymers containing 6-phenylhex-1-ene or admixed phenyl decane showed reasonably good stability against radiation, whereas the formulations containing hindered amine light stabilizers showed relatively poor radiation stability.

Silicon-carbon bridged bis(fluorenyl) and bis(octahydrofluorenyl) ansa-zirconocenes: synthesis, characterization and ethylene polymerization catalysis

The synthesis and characterization of two new silicon-carbon bridged ansa -bis(fluorenyl) and ansa -bis(octahydrofluorenyl) zirconocene complexes, (Flu−CH 2 −SiMe 2 −Flu)ZrCl 2 ( 3 ) and (FluH 8 −CH 2 −SiMe 2 −FluH 8 )ZrCl 2 ( 4 ) is reported. Complex 3 , in combination with methylaluminoxane (MAO), forms an active catalyst system for homogeneous polymerization of ethylene. The molecular structure of 4 reveals a large Centroid-Zr-Centroid angle (131.9°) and an unusually small Cl−Zr−Cl angle (93.2°). The Zr−C bond distances range from 2.48 to 2.64 A.

Glass-Transition Temperature as a Function of Conversion in Hyperbranched Polymers Obtained by Self-Condensing Vinyl Polymerization

Chain-end free volume theory is extended for studying the glass-transition temperature (T g ) as a function of conversion in hyperbranched polymers. T g is found to have a non-linear inverse relationship to the molecular weight for polymers obtained by self-condensing vinyl polymerization (SCVP). During the monomer conversion process, T g decreases with the increase in molecular weight (P) in the low conversion range, then levels off in the high conversion range.