Synthesis of (3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl) propionate derivatives and their thermal antioxidation behavior for POM

Polyoxymethylene (POM) has been widely utilized in industry due to its light weight properties in engineering plastics. At present, POM applications are expanding into the car industry, especially in fuel tanks. Hindered alkyl phenol derivatives have been used as antioxidants for POM; however, these compounds are easily extracted by solvents. Two antioxidants with new structures (N,N′‐triethylenedioxy‐bis(3‐tert‐butyl‐4‐hydroxy‐5‐methylhydrocinnamamide) and N,N′,N′‐tris[(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyl‐3‐oxapentyl]melamine) were synthesized and characterized, and their performance as antioxidants for POM was investigated in the present study. The results revealed that N,N′‐triethylenedioxy‐bis(3‐tert‐butyl‐4‐hydroxy‐5‐methylhydrocinnamamide) has good heat aging resistance compared to existing antioxidants for POM, and N,N′,N′‐tris[(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyl‐3‐oxa‐pentyl]melamine has good extraction resistance against solvents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Primary Amine‐Thioureas with Improved Catalytic Properties for “Difficult” Michael Reactions: Efficient Organocatalytic Syntheses of (S)‐Baclofen, (R)‐Baclofen and (S)‐Phenibut

Among the class of primary amine‐thioureas based on tert‐butyl esters of α‐amino acids, the most efficient organocatalyst for “difficult” Michael reactions was identified. The derivative based on (S)‐di‐tert‐butyl aspartate and (1R,2R)‐diphenylethylenediamine provided the products of the reaction between aryl methyl ketones and nitroolefins in excellent yields and enantioselectivities. In addition, this new catalyst can be used at low catalyst loading (5 mol%). The utility of this methodology was highlighted by the efficient synthesis of (S)‐baclofen, (R)‐baclofen and (S)‐phenibut.     

Thermal and Mechanical Properties of Poly(arylene ether ketone)s Based on 5‐tert‐Butyl‐1,3‐bis(4‐fluorobenzoyl)benzene

An aromatic bishalide, 5‐tert‐butyl‐1,3‐bis(4‐fluorobenzoyl)benzene ( 2 ) was synthesized in high yield and purity by the reaction of 5‐tert‐butylisophthaloyl chloride ( 1 ) and fluorobenzene and polymerized by nucleophilic substitution reaction with commercially available aromatic bisphenols to prepare a series of high molecular weight poly(arylene ether ketone)s containing pendant tertiary butyl groups. The effect of molecular structure on the physical, thermal, mechanical and adhesion properties of the polymers was investigated.     

Poly(silyl ester)s: A new route of synthesis via the condensation of Di‐tert‐butyl ester of dicarboxylic acid with dichlorosilane

Poly(silyl ester)s were synthesized by a new route via the condensation of di‐tert‐butyl ester of dicarboxylic acid with dichlorosilane by the elimination of tert‐butyl chloride as a driving force. Three new poly(silyl ester)s with molecular weights typically ranging from 2000 to 5000 amu were produced by the condensation of di‐tert‐butyl adipate with 1,5‐dichloro‐1,1,5,5‐tetramethyl‐3,3‐diphenyl trisiloxane and di‐tert‐butyl fumarate with 1,5‐dichloro‐1,1,5,5‐tetramethyl‐3,3‐diphenyl trisiloxane or 1,3‐dichlorotetramethyl disiloxane. Each polymer was characterized with infrared, ¹H‐NMR, and ¹³C‐NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. This new approach showed several advantages. First, it did not require a catalyst or solvent. Second, the tert‐butyl chloride byproduct was volatile and was easily eliminated. Third, there was no reaction between the growing poly(silyl ester)s and the condensation byproduct, tert‐butyl chloride. Fourth, the monomers could be readily purified. Finally, the polymerization could be performed at relatively low temperatures and in a short time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1378–1384, 2006     

Grafted stock synthesis of ABS at the ultimate high ratio of polybutadiene to poly(styrene‐co‐acrylonitrile)

This study describes the emulsion grafting of styrene and acrylonitrile onto 60–70% polybutadiene (PB), in the presence or absence of tert‐dodecanetiol as a chain transfer reagent with a radical initiator, and the properties of the obtained grafted stock. There was no significant difference in terms of effect of the initiation mode on the grafting efficiency resulting from the high grafting reactivity of PB. However, the grafted stock with 70% PB prepared in the presence of tert‐dodecanetiol and the adequate selection of an initiation system gave a homogeneous dispersion of the PB particles into poly(styrene‐co‐acrylonitrile) (SAN) matrix. The initiation system involves tert‐butyl peroxylaurate, tert‐butyl peroxyacetate, and tert‐butyl peroxyisopropylcarbonate coupled with ferrous sulfate. The efficient coverage of the SAN grafted layer around 70% PB particles was observed by TEM to eventually give excellent impact resistance, high surface gloss, and good thermal resistance. The absence of tert‐dodecanetiol resulted in a toughness reduction of ABS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3462–3470, 2001     

Evaluation of tert‐Butyl Isosteres: Case Studies of Physicochemical and Pharmacokinetic Properties,Efficacies, and Activities

The tert‐butyl group is a common motif in medicinal chemistry. Its incorporation into bioactive compounds is often accompanied by unwanted property modulation, such as increased lipophilicity and decreased metabolic stability. Several alternative substituents are available for the drug discovery process. Herein, physicochemical data of two series of drug analogues of bosentan and vercirnon are documented as part of a comparative study of tert‐butyl, pentafluorosulfanyl, trifluoromethyl, bicyclo[1.1.1]pentanyl, and cyclopropyl‐trifluoromethyl substituents.     

Catalytic performance of methacrylate‐based poly‐4‐(dialkylamino)‐pyridines: activity prediction via NMR shifts

The synthesis of the 4‐(dialkylamino)pyridine derivative 3‐(4‐(pyridin‐4‐yl)piperazin‐1‐yl)propyl methacrylate and its copolymerization with n‐butyl methacrylate are presented. The catalytic activity was evaluated in the acylation of tert‐butanol with acetic anhydride yielding tert‐butyl acetate. It is observed that the activity of polymer‐attached 4‐(dimethylamino)pyridine analogues correlates remarkably well with the chemical shift of the β‐pyridyl protons. Differences in catalytic efficiency result from distinct electronic densities of the pyridine ring, while embedding the catalytically active moiety into a polymeric structure has nearly no deleterious effect on the performance. © 2015 Society of Chemical Industry     

Postpolymerization of vinyl acetate‐containing latexes

The postpolymerization of vinyl acetate (VAc)‐containing latexes with tert‐butyl hydroperoxide (TBH)/ascorbic acid (AsA) as a redox initiation system was investigated. Volatile organic compounds (VOCs) such as acetone and tert‐butyl alcohol were produced in this process. The influence of the TBH/AsA ratio, initiator concentration, reaction temperature, and feeding time on the reduction of residual VAc and VOC formation during the postpolymerization was investigated. A total reduction of residual VAc monomer was achieved, with the formation of VOCs kept within acceptable limits. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 923–928, 2002     

The Copper‐Catalyzed Oxidative N‐Acylation of Sulfoximines

An oxidative cross‐coupling reaction between aldehydes and sulfoximines involving dual C H/N H functionalization has been developed. This reaction process is facilitated by a simple copper catalyst (1 mol% loading) and tert‐butyl hydroperoxide (TBHP) as the oxidant and proceeds under mild reaction conditions to afford a series of valuable N‐acylated sulfoximine derivatives in excellent yields.     

Synthesis and characterization of novel,temperature‐sensitive microgels based on N‐isopropylacrylamide and tert‐butyl acrylate

A series of temperature‐sensitive microgels based on N‐isopropylacrylamide as the main monomer, tert‐butyl acrylate (tBA) as the comonomer, and N,N′‐methylene‐bis(acrylamide) as the crosslinker were synthesized with a modified surfactant‐free emulsion polymerization method. The chemical structure and global shape with an excellent monodispersity of the microgels were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The temperature‐sensitive behavior of the microgels was investigated by dynamic light scattering and ultraviolet–visible spectrophotometric analysis. The results show that the volume phase‐transition temperature of the poly(N‐isopropylacrylamide‐co‐tert‐butyl acrylate) [poly(NIPAM‐co‐tBA)] microgels were tuned over a broad range by the incorporated amount of tBA comonomer and their temperature sensitivity decreased with increasing content of tBA units incorporated into the microgel network. Furthermore, the swelling ratios of the poly (NIPAM‐co‐tBA) microgels were lowered gradually with increasing tBA unit content within the microgel network. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2962–2967, 2007     

Water‐dispersible porous polyisoprene‐block‐poly(acrylic acid) microspheres

Two polyisoprene‐block‐poly(tert‐butyl acrylate) (PI‐b‐PtBA) samples and a poly(tert‐butyl acrylate) (PtBA) homopolymer (hPtBA) were prepared by anionic polymerization and characterized by light scattering, size exclusion chromatography, and NMR. The tert‐butyl groups were removed from one of the diblocks to yield amphiphilic polyisoprene‐block‐poly(acrylic acid) (PI‐b‐PAA). PI‐b‐PAA was then used as the surfactant to disperse dichloromethane containing PI‐b‐PtBA and hPtBA at different weight ratios as oil droplets in water. Solid microspheres containing segregated polyisoprene (PI) and PtBA/hPtBA domains were obtained after dichloromethane evaporation. Permanent microspheres were obtained after PI domain crosslinking with sulfur monochloride. Porous microspheres were produced after the hydrolysis of PtBA and the extraction of the homopoly(acrylic acid) chains. The shape and connectivity of the poly(acrylic acid)‐lined pores were tuned by changes in the PtBA/hPtBA content in the precursor microspheres. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2785–2793, 2003     

Vanadium‐Catalyzed Selective Oxidation of Alcohols to Aldehydes and Ketones with tert‐Butyl Hydroperoxide

The oxidation of alcohols to aldehydes and ketones has been described using silica‐supported vanadium(IV ) oxide (V/SiO₂, 1 ) in the presence of tert‐butyl hydroperoxide in tert‐butyl alcohol at ambient temperature with quantitative yields. The procedure is simple, efficient and environmentally benign.     

Peroxide macro‐initiators for improving biodegradability of polymers

Modification of dextrin by tert‐butylperoxy methanol or its acylation with cyclic anhydride containing a peroxide group resulted in macro‐initiators with randomly located peroxide fragments in the polysaccharide. When dextran was oxidized with iodic acid, dialdehydedextran was obtained. Its aldehyde groups reacted with tert‐butyl hydroperoxide to give functional peroxide groups. The content of peroxide fragments depended directly on the ratio of reagents. The resulting macro‐initiators may be used for synthesizing graft copolymers with polystyrene on poly(butyl acrylate) containing polysaccharide. © 2001 Society of Chemical Industry     

Graft copolymers from commercial chlorinated polypropylene via Cu(0)‐mediated atom transfer radical polymerization

Commercially available chlorinated polypropylene has been used as a macroinitiator for the Cu(0)‐mediated atom transfer radical polymerization of methyl methacrylate and tert‐butyl acrylate to obtain well‐defined graft copolymers. The relatively narrow molecular weight distribution in the graft copolymers and linear kinetic plots indicated the controlled nature of the copolymerization reactions. Both Fourier transform infrared and ¹H NMR studies confirmed that the graft reactions had taken place successfully. After graft copolymer formation, tert‐butyl groups of poly(tert‐butyl acrylate) side chains were completely converted into poly(acrylic acid) chains to afford corresponding amphiphilic graft copolymers. © 2016 Society of Chemical Industry     

Antioxidant mechanism of a 3‐arylbenzofuranone containing a 2′‐hydroxyl group

5‐Methyl‐7‐tert‐butyl‐3‐(2′hydroxyl‐5′‐methylphenyl)3H‐benzofuran‐2‐one (PCRBF2), is a better scavenger of 2,2‐diphenyl‐1‐picrylhydrazyl radicals than benzofuranone analogs without the 2′‐substituent, which indicates that PCRBF2 will cause good stabilization in polymers. To prove this further, antioxidation by PCRBF2 and other benzofuranone analogs, namely, 5‐methyl‐7‐tert‐butyl‐3‐(3′,4′‐dimethylphenyl)3H‐benzofuran‐2‐one (OXBF2) and 5‐methyl‐7‐tert‐butyl‐3‐(2′,5′‐dimethylphenyl)3H‐benzofuran‐2‐one (PXBF2), was comparatively studied in polypropylene. The resulting antioxidant activity order of these benzofuranones was PCRBF2 > OXBF2 > PXBF2, an observation showing that the hydroxyl group in the 2′‐position does not weaken the antioxidant activity of benzofuranone, but, on the contrary, increases it. Analyses by FTIR revealed intramolecular hydrogen bonding between the 3‐position hydrogen and the oxygen of the 2′‐hydroxyl group, which makes the 2′‐hydroxyl hydrogen of PCRBF2 more reactive than the 3‐position reactive hydrogen. Thus the hydroxyl group reacts with radicals first. J. VINYL ADDIT. TECHNOL., 19:198‐202, 2013. © 2013 Society of Plastics Engineers     

Preparation and characterization of poly(silyl ester)s containing 2,2‐bis(p‐dimethylsiloxy‐phenyl)propane units in the polymer backbones

The two poly(silyl ester)s containing 2,2‐bis(p‐dimethylsiloxy‐phenyl)propane units in the polymer backbones have been prepared via polycondensation reaction of di‐tert‐butyl adipate and di‐tert‐butyl fumarate with 2,2‐bis(p‐chloro dimethylsiloxy‐phenyl)propane to give tert‐butyl chloride as the condensate. The polymerizations were performed under nitrogen at 110°C for 24 h without addition of solvents and catalysts to obtain the poly(silyl ester)s with weight average molecular weights typically ranging from 5000 to 10,000 g/mol. Characterization of the poly(silyl ester)s included ¹H NMR and ¹³C NMR spectroscopies, infrared spectroscopy, ultraviolet spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TGA), gel permeation chromatography, and Ubbelohde viscometer. The glass transition temperatures (T_g) of the obtained polymers were above zero because of the introducing 2,2‐bis(p‐dimethylsiloxy‐phenyl)propane units in the polymer backbones. The TGA/DTG results showed that the obtained poly(silyl ester)s were stable up to 180°C and the residual weight percent at 800°C were 18 and 9%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1937–1942, 2006     

Reactions and polymerization of hexa‐[3‐tert‐butyl‐4‐ hydroxyphenoxy]cyclotriphosphazene: A new method for the preparation of soluble cyclomatrix phosphazene polymers

Novel cyclomatrix phosphazene‐containing polyester polymers were synthesized through the reaction of a polyhydroxylated cyclotriphosphazene and a bifunctional acid chloride. To demonstrate the chemistry of the free hydroxyl of hexa‐[3‐tert‐butyl‐4‐hydroxyphenoxy]cyclotriphosphazene, nucleophilic displacement reactions were performed with both acetic anhydride and alkyl chlorides. This work compares favorably to literature data for the chemistry of hexa‐[4‐hydroxyphenoxy]cyclotriphosphazene, whose hydroxyl is not hindered by an adjacent substituent. The hindered site of hexa‐[3‐tert‐butyl‐4‐hydroxyphenoxy]cyclotriphosphazene was found to react with bidentate acid chlorides to yield new high polymers. The phosphazene‐containing polyesters were observed to have good solubility in polar organic solvents. Characterization of these new materials was performed using dilute solution laser light scattering techniques, thermal analysis, and NMR spectroscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 242–251, 2001     

Dielectric properties of new fully conjugated 2H‐ and metal‐pyrazinoporphyrazine network polymers

2,7‐Di‐tert‐butylpyrene was oxidized to 2,7‐di‐tert‐butylpyrene‐4,5,9,10‐tetraone. The latter through condensation reaction with vicinal diamine such as diaminomaleodinitrile afforded heterocyclic monomer, 2,7‐di‐tert‐butyl pyrene[4,5][9,10]bis(2,3‐pyrazine‐5,6‐dinitrile), which was cyclotetramerized to the corresponding 2H‐ and metal‐pyrazinoporphyrazine‐based network polymers (2H‐PyzPz and M‐PyzPz, M = Co, Ni, Zn, or Cu). Elemental analytical results, Infrared, and NMR spectral data of the new prepared molecules are consistent with their assigned formulations. Molecular masses and metal contents of the synthesized polymers proved to be of high molecular masses, which confirm the efficiency of tetramerization polymerization and complexation reactions. Dielectric permittivity, ε′, loss tangent, tan δ, and ac conductivity, σac(ω), of 2H‐PyzPz and M‐PyzPz films were studied as a function of temperature and frequency. It was found that dielectric permittivity, ε′, decreases with the increase of frequency and increases with the increase in temperature. Ac conductivity, σac(ω), is found to vary as Bωs and the frequency exponent, s, is less than unity around room temperature indicating a dominant hopping process. On the other hand, σac(T) of all samples is thermally activated with low activation energies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Functionalization of high‐density polyethylene in the molten state by glycidyl methacrylate grafting

:This study concerns the melt‐free radical grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene (HDPE). We studied the effect of two initiators (tert‐butyl cumyl peroxide and di‐tert‐butyl peroxide) onto HDPE. Crosslinking of polymer was observed in the presence of 0.3 wt % tert‐butyl cumyl peroxide but not with 0.3 wt % di‐tert‐butyl peroxide. The grafting was carried out in a Brabender batch mixer at 190 °C. The grafting yield of GMA onto HDPE (determined by infrared spectrometry) is weak (<1 wt % for an initial concentration in monomer of 6 wt %). Moreover, it was noted that the degree of grafting did not vary with the concentration and the nature of peroxide used. To increase the grafting yield of GMA, we added to the HDPE/peroxide/GMA system an electron‐donating monomer, such as styrene. Adding this comonomer multiplied the rate of grafted GMA 3‐ or 4‐fold, resulting in a ratio [styrene]_i/[GMA]_i = 1 mol/mol with [GMA]_i = 6 wt %. So, the copolymerization is favored compared with the homopolymerization. This kind of copolymer presenting reactive functions is very attractive in the field of compatibilizing immiscible polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 581–590, 2001     

A molecularly imprinted polymer via a salicylaldiminato‐based cobalt(III) complex: A highly selective solid‐phase extractant for anionic reactive dyes

A novel molecularly imprinted polymer based on tert‐butyl acrylate (MIP‐BA) was fabricated with the assistance of a cobalt(III)‐based catalyst bearing an N‐salicylidene isopropylamine ligand [(SPA)₂CoCl]. After initiation with methyl aluminoxane, the catalyst system was found to be active toward the polymerization of tert‐butyl acrylate (t‐BA) in the presence of a polar template (Cibacron reactive red dye) and divinylbenzene (DVB) as a crosslinker. Polymerization experiments, including those of t‐BA, t‐BA, and DVB and t‐BA and dye, were also carried out. Isolated blank polymers and MIP‐BA were analyzed with a variety of techniques, including differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography, infrared spectroscopy, nuclear magnetic resonance, and ultraviolet–visible spectroscopy. In general, the complex showed moderate polymerization activity and produced high‐molar‐mass poly(tert‐butyl acrylate); however, a decrease in the monomer conversion was observed upon the addition of the dye and/or the crosslinker. The effect of imprinting was obvious when the adsorption capacity of MIP‐BA measured at pH 6 for red dye (the imprinted molecule) was increased from 9.2 to 90.4 mg/g after imprinting. Competitive adsorption studies revealed that the dye‐imprinted polymer enabled the efficient uptake of red dye, even in the presence of blue and yellow dyes that had similar chemical structures to the imprinted molecule. The selectivity coefficients were 43 and 36 with respect to the blue and yellow dyes, respectively. The proposed polymerization procedure could be extended to other anionic polar reactive dyes and polar reactive polymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010