Polymerization behavior of 1,2,2,6,6-pentamethyl-4-piperidinyl m-isopropenyl-α,α-dimethylbenzyl carbamate

Copolymers of 1,2,2,6,6-pentamethyl-4-piperidinyl m-isopropenyl-α,α-dimethylbenzyl carbamate (CB) with styrene (S) and with methyl methacrylate (MMA) were synthesized using AIBN as initiator. S–CB copolymers made from feed ranging from 0.45–0.94 mole fractions S and MMA-CB copolymers made from feed of 0.34–0.88 mole fractions MMA were used to determine the monomer reactivity ratios r₁ and r₂. The structure of S–CB copolymers was inferred to be mainly of a random nature and in the MMA–CB copolymerization system there is a stronger tendency to form alternating copolymers. © 1993 John Wiley & Sons, Inc.     

Hydrosilylation of m-TMI: New siloxane based aliphatic polyisocynates

Well-characterized polyfunctional aliphatic isocyanates were obtained in high purity and quantitative yield by the hydrosilylation of m-isopropenyl-α,α-dimethylbenzyl isocyanate (m-TMI) with cyclic and acyclic hydrogementhylsiloxance. The products were characterized by ¹H- and ¹³C-NMR, IR, and GPC, and all result exclusively from ß-addition to m-TMI. Polymers with SiH Groups are also effective hydrosilylating agents of m-TMI. The isocyanato siloxanes can be used as precursors for star and network polymers as well as other poly-functional reagents, and examples of reactions with methoxy polyethylene glycol and with amine-containing compounds are discussed.     

Surface-Anchored Hindered-Amine Light Stabilizers for Improved UV Stability of Polyolefins

Abstract

Hindered-amine light stabilizers (HALS) were surface anchored to polyolefin films by reacting the HALS, namely, 1,2,2,6,6-pentamethyl-4-piperidinol and 1,2,2,6,6-pentamethyl-4-aminopiperidine, with succinic anhydride functionalized polyolefin surfaces. The photostability of polyolefin films with surface-anchored HALS were compared with films stabilized with commercial HALS (Tinuvin 770) by melt blending. It is shown that the photostabilizing efficiency of surface-anchored HALS is superior that of melt-blended polyolefins.     

Synthesis and properties of α-substituted benzylpyridinium salts as cationic initiators

α-Methylbenzylpyridinium SbF₆ (1a) and α,α-dimethylbenzylpyridinium SbF₆ (1b) were prepared and the effect of α-methyl groups on the active species and the activity of 1a, 1b during the cationic polymerization of glycidyl phenyl ether (GPE) was evaluated. 1b was prepared by the reaction of α,α-dimethylbenzyl alcohol with pyridinium hexafluoroantimonate (2) in several solvents, and the yield depended on the dipole moment of the solvents, although it was poor for the reaction of α,α-dimethylbenzyl chloride with pyridine for the steric hindrance of the α-methyl groups followed by exchange with NaSbF₆. Both 1a and 1b acted as a latent thermal initiator during the cationic polymerization of GPE and 1b showed higher activity during cationic polymerization with the higher steric effect of the α-methyl groups than 1a. The ¹H-NMR analysis of the obtained poly GPE indicated that the active species of 1b changed from the benzyl cation to H⁺, depending on the reaction temperature, although 1a released benzyl cations as active species in the cationic polymerization of GPE. © 1996 John Wiley & Sons, Inc.     

Preparation of a novel HALS polypropylene stabilizer

The radiation induced graft copolymerization of m-isopropenyl-α,α-dimethyl benzyl iso-cyanate (m-TMI) and styrene onto polypropylene was carried out. The extent of grafting increased with increasing amount of styrene and with increased radiation dose. A graft load of 180% was obtained by immersing a 50 kGy pre-irradiated film in a monomer solution containing 25 mol % m-TMI and 75 mol % styrene. The graft copolymer is suitable for covalently binding nonpolymerizable stabilizers with a suitable nucleophilic moiety. In this work the isocyanate moiety of the graft copolymer was allowed to react with 4-amino-2,2,6,6-tetramethyl piperidine, a hindered amine light stabilizer. Fourier trans-formed infrared spectroscopy confirmed the formation of an urea moiety. © 1995 John Wiley & Sons, Inc.     

Low molar mass polybutadiene made crosslinkable by the introduction of styrenic moieties via urethane linkage: synthesis, kinetic and crosslinking studies

The introduction of styrenic moieties was chosen for the radical crosslinking of polybutadiene bearing hydroxy functions. The modifications were carried out with 3-isopropenyl-α,α-dimethylbenzyl isocyanate (TMI) with or without catalyst (DBTL). A 2nd order kinetic fits our experimental results up to high conversion. Arrhenius parameters were calculated. Thermally catalyzed crosslinking was studied. The reaction was followed by measuring swelling (Q) in toluene as well as mechanical parameters (storage modulus E^′ at the rubbery plateau and tanδ). The influence of temperature, the nature and concentration of initiators, the number of styrenic groups per chain (n=1.2, 2, 2.4) were investigated. In the range of our experimental conditions, a “reaction master curve” was established to predict the evolution of E^′ and Q as a function of time, for any temperature, initiator concentration and value of n.     

Linear polybenzyls. III. Sterically assisted linear polymerization of 2,5-dimethylbenzyl chloride and α-methylbenzyl chloride

The low-temperature Friedel-Crafts step-growth polymerization reactions of 2,5-dimethylbenzyl chloride with TiCl₄—(C₂H₅)₂AlCl catalyst, and of α-methylbenzyl chloride with AlCl₃ catalyst were investigated for the effect of reaction conditions on polymer molecular weight, linearity, glass transition temperature, and crystalline properties. Premature precipitation of highly crystalline poly(2,5-dimethylbenzyl) prevented the preparation of high molecular weight products from this monomer, while most likely an indanyl-type termination reaction limited the molecular weight of poly(α-methylbenzyl). Model reactions indicated that, under proper conditions, the latter could be prepared with 99% para substitution, and these polymers were crystalline.     

TADDOLs with Unprecedented Helical Twisting Power in Liquid Crystals. Preliminary communication

A large number of TADDOL (α,α,α′, α′-tetraaryl-1,3-dioxolan-4,5-dimethanol) derivatives has been tested as chiral dopants for inducing conversion of nematic to cholesteric phases. With the Merck liquid-crystal materials ZLI-1695 and K15 , it was demonstrated that some TADDOLs have unprecedentedly high helical twisting powers (HTP). Thus, the TADDOL with four 9-phenanthryl α-substituents has a HTP in the achiral mesophase 4-(4-pentylphenyl)benzonitrile of 405 μm^?1 between 24 and 34°. The temperature-dependent HTP measurements have been performed by analyzing Grandjean textures microscopically (Cano method). The structure-dependent HTP of various types of TADDOL dopants is discussed. There are similarities between size and sign of HTP on the one hand, and between degree and relative topicity of enantioselectivity in reactions, on the other hand, as caused by TADDOLs and by 1,1′-binaphthols.     

proton transfers of substituted ammonium salts—XIII : N-inversion of piperidines in aqueous acidic solutions

The kinetics of the nitrogen inversion of 1,2-dimethyl-(2); 1,4-dimethyl-(8); 1-trans(2,6)-trimethyl-(4); 1,4-cis(2,6)-tetramethyl-(7) and 1,2,2,6,6-pentamethyl-(5)piperidines have been investigated in aqueous acidic solution (pH = 6.5–8.5) at 33° by dynamic NMR. In all cases, two isomeric cations AH⁺ and BH⁺ are observed in acidic conditions (pH<6?), and the nitrogen inversion is brought to the NMR time scale as a result of a progressive deprotonation of the cations into their conjugate amines on increasing the pH. Low rate constants K_A are obtained for α-substituted or unsubstituted compounds (k_A ?10³ s^?1), except for piperidine 5 where the rate constant k_A = 4.3 × 10⁵ s^?1 is of the same order of magnitude as the one found for tertiary acyclic amines.     

Photostabilising effect of bis(hindered piperidine) compounds: Part I—In photo-oxidative degradation of cis-1,4-poly(butadiene)

The photostabilizing effect of three commercially available bis(hindered piperidines): Tinuvin 144 (bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-2-n-butyl-2-(3,5-di-tert-butyl-4-hydroxy-benzyl) malonate; Tinuvin 292 (bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate) and Tinuvin 770 (bis(2,2,6,6-tetramethyl 14-piperidinyl) sebacate) on the free radical photo-oxidative degradation of cis-1,4-polybutadiene has been investigated. Their stabilising effects include possible mechanisms such as formation of bis(hindered nitroxyl radicals), which then scavenge polymer alkyl radicals produced during photo-oxidation. Bis(hindered piperidines) may also decompose hydroperoxide groups. The most effective stabiliser of the three was Tinuvin 144 and the least effective was Tinuvin 770.     

Novel carbamoyl phosphonate monomers and polymers from unsaturated isocyanates

Carbamoyl phosphonate derivatives of methacrylic acid and α-methyl styrene were synthesized in good yield by reacting dimethyl and diethylphosphite with isocyanato ethylmethacrylate (IEM) or with meta-isopropenyl-α,α-dimethylbenzylisocyanate (m-TMI). The IEM derivatives yield soluble homopolymers with common radical initiators. The m-TMI carbamoyl phosphonates were copolymerized with styrene and with acrylates yielding soluble materials with better than 50 mol % incorporation of the phosphonate monomer. The side chain carbamoyl phosphonate group drastically lowers the T_g relative to those of the parent polymers. Thermogravimetric studies suggest the NHC(O)? P(O)(OR)₂ bond to be stable to about 225°C. The radiopacifying salt UO₂(NO₃)₂6 H₂O yields transparent films with the phosphonate-containing polymers. The T_g increases with uranyl content. © 1993 John Wiley & Sons, Inc.     

Study of photocrosslinkable polysiloxanes bearing gem di-styrenyl groups: Synthesis and thermal properties

The synthesis of photocrosslinkable polysiloxanes containing gem di-oxaalkylene styrenyl groups and gem di-urethane-α-methyl styrenyl groups has been performed by copolycondensation of α,ω-dihydroxy polydimethyl siloxanes and dichlorosilanes bearing either cyclic acetal groups or Si-H groups (onto which the cyclic acetal groups are further added) and dichlorosilanes bearing alkyl groups. The introduction of styrenyl groups was then achieved by hydrolysis of the acetal groups into the corresponding alcohols followed by reaction with chloromethyl styrene or with 3-isopropenyl-α,α- dimethylbenzyl isocyanate.The structure of the different products synthesized was determined by IR, ¹H, ¹³C and ²⁹Si NMR spectroscopies. The thermal properties of the polysiloxanes bearing gem di-styrenyl groups have been studied at low and high temperatures.These products have been crosslinked under UV, in the presence of a cationic photoinitiator, and showed very good release paper properties.     

The reactivity of 3,5-dimethylidene-2,2,6,6-tetramethyl-4-oxopiperidin-1-oxyl and its diamagneticN-methyl analog in nucleophilic addition of amines and diels—Alder dimerization

3,5-Dimethylidene-1,2,2,6,6-pentamethyl-4-oxopiperidine was shown by the kinetic method to be less reactive than 3,5-dimethylidene-2,2,6,6-tetramethyl-4-oxopiperidin-1-oxyl in the nucleophilic addition of secondary amines and Diels—Alder dimerization. According to the quantum-chemical AM1 calculations, this is due to the difference in the structures of the activated complexes (in the reactions with amines) and to the “press” effect created by theN-methyl group that impedes the necessary cycle flattening (in the Diels—Alder reaction). Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1698–1702, October, 2000.     

The 4α-Methylsterol Violasterol A from Viola Formosana Hayata

A new 4α-methylsterol, violasterol A, with three known flavonoids-luteolin, luteolin 7-O-β-D-glucoside and tricin-were isolated from ethanolic extract of whole plants of Viola formosana. The structure of vioiasterol A was assigned to be (22E)-4α-methyl-24ξ-isopropenyl-5α-cholesta-7, 22-diene-3β-ol (1) on the basis of spectral and chemical evidence.     

Mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones and their derivatives

The mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones (compounds 1) and their 2,4-dinitrophenylhydrazones (compounds 2) and semicarbazones (compounds 3) have been studied. The characteristic fragments at m/z (M ? 73) from compounds 1, m/z (M ? 253) from compounds 2 and m/z (M ? 130) from compounds 3 are abundant and proposed to be [ArCROCH₃]⁺. Fragmentations yielding [M⁺ ? 49] from compounds 2 are abnormal and probably involve the methoxyl and nitro groups. The intense peak at m/z 130 due to [CH₃OCH₂CNNHCONH₂]⁺ from compounds 3 corresponds to α-cleavage of the molecular ion. Some other fragments from these new compounds are interpreted in this paper.     

Diazoniapentaphenes. Synthesis from pyridine‐2‐carboxaldehyde and structural verifications

Reactions of pyridine‐2‐carboxaldehyde (9) with α,α′‐dibromo‐o‐ and p‐xylenes led to the corresponding bis‐pyridinium aldehydes 10 and 14. These aldehydes were quite reactive and the respective hydrates 11 and 15 were also formed. Cyclization of 10 or 11 with 48% HBr led to 12 while cyclization with PPA followed by conversion to the bis tribromide and loss of bromine led to 1. Cyclization of 14 or 15 with 48% HBr led to 3. Attempts to react α,α′‐dibromo‐m‐xylene with pyridine‐2‐carboxaldehyde (9) were not successful for the preparation of the bis‐pyridinium aldehyde 13. The bis‐pyridinium acetals 4, 5 and 6 were prepared and cyclized to afford 1, 2 and 3 , respectively, by the previously reported procedures. The structures of 1 and 2 were verified by ¹H‐NMR and ¹³C‐NMR spectroscopy while that of 3 was confirmed by X‐ray analysis.     

Melanotropin Receptors II. Synthesis and Biological Activity of α-Melanotropin/Tobacco Mosaic Virus Disulfide Conjugates

Asymmetric disulfide conjugates of mercaptosuccinyl tobacco mosaic virus (TMV ～ SH) with N^α-desacetyl-N^α-5-(mercaptovaleryl)-α-melanotropin were prepared via the S-sulfoderivative of the peptide. The conjugates, TMV ～ S? S ～ α-MSH(n), contained up to n = 330 disulfide-linked peptide molecules/virion. Similarly, fluorescent conjugates, Rh(m) ～ TMV ～ S? S ～ α-MSH(n) were prepared, containing m ≈? 200 rhodamine molecules linked to the virions by thiourea bridges. Such conjugates were designed to study α-MSH receptor localization and dynamics (mainly internalization), because the carrier virions which served to enhance specific receptor binding and as fluorescent or radioactive markers may be detached from the neuropeptides at will by reduction. Reduction occurred in solution and on the cell surface, but not in the cytoplasm, thus allowing detection of internalized agonist-receptor complexes. The conjugates were superpotent agonists for tyrosinase stimulation in Cloudman S-91 melanoma cell cultures, but were inactive for cyclic AMP accumulation. Their rather rapid internalization and the influence of reducing agents and other agonists on their biologic activity suggest a close connection between receptor location and biologic response as well as the presence of essential receptor HS-groups.     

Isolation and structural characterization of a low-molecular-weight pectic polysaccharide SHPPB-1 isolated from sunflower heads

A novel low-molecular-weight pectic polysaccharide was isolated from sunflower heads that are a useless side product produced from sunflower oil processing. The low-molecular-weight pectic polysaccharide was purified by using an optimized four-step procedure and named as SHPPB-1. The molecular weight of SHPPB-1 is about 1.69× 10⁴ Da. Structure characterizations of SHPPB-1 by monosaccharide composition, methylation analysis, and Fourier transform infrared (FT-IR) spectroscopy showed that SHPPB-1 is consisted of 1,4-linked α-D-GalpA and 1,4-linked 2-OAc-5-COOMe-α-D-GalpA with rare α/β-D-Rhap, α/β-D-Manp, and α/β-D-GalpA. This was combined with NMR spectroscopic analysis to propose a structure of SHPPB-1 as: →4)-[α/β-D-monosaccharide-(1→3)]-α-D-GalpA-(1→4)-2-OAc-5-COOMe-α-D-GalpA-(1→ .     

Syntheses and reactions of optically active polymers. II. Preparations of optically active polymers containing quinine,L-ephedrine,and L-histidine residues and their reactions with α-cyanoethylaquocobaloxime

Preparations of polymers with bis(dimethylglyoximato)cobalt (cobaloxime) were investigated. 4-Vinylpyridine was reacted with α-cyanoethylaquocobaloxime to produce α-cyanoethyl-4-vinylpyridinatocobaloxime (I) in 72% yield. It did not, however, polymerize by the use of azobisisobutyronitrile (AIBN) as an initiator. Polymers containing α-cyanoethylcobaloxime were obtained by reactions of polymers with α-cyanoethylaquocobaloxime (II). Poly(9-O-methacryloylquinine) (III), poly(O-methacryloyl-N-methyl-L -ephedrine) (IV), poly[N^α-(o-vinylbenzyl)-L -histidine] (V), and poly(4-vinylpyridine) (VI) were prepared and used in these reactions. Polymers V and VI were reacted with II to give polymers X, XI, XII, and XIII containing α-cyanoethylcobaloxime.     

Determination of the Components of the Boll Weevil Pheromone with a High Pressure Liquid Chromotographic Method

Abstract

A high pressure liquid chromatographic method was developed to separate the 4 components of the pheromone of the boll weevil. Minimum detectable amounts with 3.5% tetrahydrofuran in hexane was 10 ng for (+)-cis-2-isopropenyl-1-methyl-cyclobutaneethanol, 1 ng for (Z)-3,3-dimethyl-Δ¹,α-cyclohexaneethenol, and 2.5 ng each for (Z)-3,3-dimethyl-Δ¹,α-cyclohexaneacetaldehyde and (E)-3,3-dimethyl -Δ¹α-cyclohexaneacetaldehyde at 214 nm.