Tert-butyl Peroxypivalate Research Articles

End-Group Control in the Radical Polymerization of Methyl Methacrylate with tert-Butyl Peroxypivalate Initiator in the Presence of Thiol Chain Transfer Agents

The radical polymerization of methyl methacrylate (MMA) by the thermal initiator tert-butyl peroxypivalate (tBPPiv) and in the presence of various thiol-containing chain transfer agents (CTAs) has ...

Investigation of the Chain Transfer Agent Effect on the Polymerization of Vinylidene Fluoride

The effect of chain transfer agents (CTAs) ethyl acetate (EA), octyl acetate (OA), and isopropyl alcohol (IPA) on the rate of polymerization of vinylidene fluoride (VDF) in an emulsion polymerization and in solution polymerization in dimethyl carbonate (DMC) initiated by tert-butyl peroxypivalate was investigated. Pressure profiles of the polymerizations were recorded. Solids content and rate of polymerization were calculated by gravimetry; size exclusion chromatography was utilized to evaluate CTA activity, and the produced polymer microstructures were characterized by 1H and 19F NMR spectroscopies. It is proposed that the observed reduction in polymerization rate in both systems is due to degradative chain transfer reactions.

Properties of single-component acrylic pressure-sensitive adhesives synthesized using tert-butyl peroxypivalate initiator

In this work, tert-butyl peroxypivalate initiator was newly used in the solution polymerization of acrylic copolymers with 2-ethylhexyl acrylate, butyl acrylate, methyl methacrylate and acrylic acid monomers for application of pressure-sensitive adhesives (PSAs). Its proper dosage was determined to vary from 0.6 to 1.2 wt % when a high monomer conversion (>99%) was ensured. In this amount range, polymer properties and adhesive performance of the PSAs were investigated. The results indicated that with the amount of tert-butyl peroxypivalate increased, the molecular weights of the polymer decreased and the molecular weight distribution became wider. It was also observed that the synthesized PSAs had high interfacial adhesion and low cohesion strength, and thus exhibited cohesive failure during the peel test. So cross-linking agent was employed to improve the shear strength of the PSAs and to eliminate the adhesive residue while at the sacrifice of loop tack and peel strength. As a whole, the optimal performance was obtained by using 1.2 wt % amount of initiator and 0.5 wt % concentration of cross-linker. In this case, the peel and shear strength have achieved the best balance. In addition, for the cross-linked PSA tapes, the peel strength slightly decreased with the dwell time.

Microreactors-A Powerful Tool to Synthesize Peroxycarboxylic Esters.

The synthesis of peroxycarboxylic esters, as one subgroup of organic peroxides, is characterized by a high thermal hazard potential regarding process safety. In case of failure in the production process, e.g., if the heat of reaction cannot be removed sufficiently fast, decomposition reactions can be triggered, and as a result, remarkable amounts of heat and gas can be released and can cause a high extent of damage. Multifarious technical and organizational measures are necessary to ensure the safe industrial production of peroxides. With the introduction of microreaction technology plenty of possibilities have been opened to carry out highly exothermic reactions in smaller volumes and with more efficient heat removal. In this paper we report the application of three different microstructured reactors, representing different mixing strategies, to synthesize two peroxymonocarboxylic esters, namely tert-butyl peroxypivalate and tert-butyl peroxy-2-ethylhexanoate. The following reactor types were considered: an orifice microreactor, a split and recombine microreactor and a capillary tube reactor in combination with ultrasonication. The efficiency of the two phase liquid/liquid reaction is expressed in comparison of conversion and selectivity. With microreaction technology a remarkable increase in space-time-yield, ranging from 12,500 kg·m−3·h−1 to 414,000 kg·m−3·h−1, is achieved.

Radical Copolymerization of Vinylidene Fluoride (VDF) with Oligo(hexafluoropropylene oxide) Perfluorovinyl Ether Macromonomer To Obtain PVDF-g-oligo(HFPO) Graft Copolymers

The synthesis of PVDF-g-oligo(HFPO) graft copolymers, where VDF and HFPO stand for vinylidene fluoride and hexafluoropropylene oxide, respectively, is presented. First, an oligo(HFPO)–OCF═CF2 macromonomer was prepared from two methods starting from oligo(HFPO) acyl fluoride in 34 to 54% yield. Then, the radical copolymerization of VDF with that comonomer, initiated by tert-butyl peroxypivalate (TBPPi) or perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical (PPFR) was studied under various conditions. The resulting PVDF-g-oligo(HFPO) graft copolymers were produced in good isolated yields (74 to 89%). The molar percentages and molecular weights of the graft copolymers were assessed by 19F and 1H NMR spectroscopy. Molar percentages of VDF and oligo(HFPO)–OCF═CF2 comonomers reached up to 99% and 11%, respectively, while the molecular weights ranged from 25 000 to 77 000 g/mol. Their thermal properties were also studied and showed: (1) satisfactory thermostability (Td) in the 410 to 494 °C range under ai...

Synthesis and characterizations of alternating co- and terpolymers based on vinyl ethers and chlorotrifluoroethylene

The synthesis of new terpolymers based on chlorotrifluoroethylene (CTFE), 2-chloroethylvinyl ether (CEVE) and 1H,1H,2H,2H-perfluorodecyl vinyl ether (FAVE8), in 1,1,1,3,3-pentafluorobutane initiated by tert-butylperoxypivalate (TBPPI) and CF3˙ radicals is presented. The products were obtained in high yields and their composition was assessed by 1H and 19F NMR spectroscopy and elemental analysis, confirming the very good alternation between CTFE and vinyl ether (VE) monomeric units. The molecular weights of the resulting products were determined by size exclusion chromatography and their thermal properties, i.e. degradation temperature under air and glass transition temperature (Tg), were also assessed. The introduction of the fluorinated vinyl ether in the terpolymers did affect the thermal stability and induced a linear decrease of the Tg values of the resulting materials. Films were also cast from acetone to carry out water contact angle measurements that were higher for higher FAVE8 contents.

Synthesis and characterization of original alternated fluorinated copolymers bearing glycidyl carbonate side groups

AbstractA vinyl ether bearing a carbonate side group (2‐oxo‐1,3‐dioxolan‐4‐yl‐methyl vinyl ether, GCVE) was synthesized and copolymerized with various commercially available fluoroolefins [chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and perfluoromethyl vinyl ether (PMVE)] by radical copolymerization initiated by tert‐butyl peroxypivalate. Although HFP, PMVE, and vinyl ether do not homopolymerize under radical conditions, they copolymerized easily yielding alternating poly(GCVE‐alt‐F‐alkene) copolymers. These alternating structures were confirmed by elemental analysis as well as 1H, 19F, and 13C NMR spectroscopy. All copolymers were obtained in good yield (73–85%), with molecular weights ranging from 3900 to 4600 g mol−1 and polydispersities below 2.0. Their thermogravimetric analyses under air showed decomposition temperatures at 10% weight loss (Td,10%) in the 284–330°C range. The HFP‐based copolymer exhibited a better thermal stability than those based on CTFE and PMVE. The glass transition temperatures were in the 15–65°C range. These original copolymers may find potential interest as polymer electrolytes in lithium ions batteries. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Continuous Synthesis of tert‐Butyl Peroxypivalate using a Single‐Channel Microreactor Equipped with Orifices as Emulsification Units

The two-step synthesis of tert-butyl peroxypivalate is performed in a single-channel microreactor. The first step, the deprotonation of tert-butyl hydroperoxide, is done in a simple mixer tube setup. The residence time section for the second reaction step is equipped with orifices for interfacial area renewal, needed for ensuring mass transfer between the two immiscible phases. The strong dependence of the reaction performance on the size of the interfacial area is demonstrated by using a setup with 4 orifices (distance of 52 cm), giving a HPLC yield of 71% at a residence time of 8 s and a reaction temperature of 23 °C. A further shortening of orifice distances helped to shorten the residence time down to 1.5 s and 0.5 s (using 9 orifices and 3 orifices with a distance of 5 cm). When using these setups, the produced heat could not be removed from the system sufficiently quickly (ΔT=38 K). The achieved yields (ca. 70% by HPLC) are close to the state of the art (cascaded batch processing) and provide an indication that the tert-butyl peroxypivalate synthesis can be performed at higher temperatures or at least, a more flexible process control can be allowed compared to high-volume batch reactors. Processing at higher reaction temperatures up to 70 °C shows a slight optimum at reaction temperatures between 40 °C to 50 °C, depending on the setup used. Knowing this novel process window as well as the optimum orifice geometry and distance will allow for tailored design of the microreactor. For the processing in the single-channel microreactor setup using 9 orifices (distance of 5 cm) and a reaction temperature of 40 °C a space-time-yield of 420,000 g L(-1) h(-1) was reached which is higher than the space-time-yield for the industrial 3 cascaded batch reactor process (190 g L(-1) h(-1)).

Radical Copolymerization of α,β-Difluoroacrylic Acid with Vinylidene Fluoride.

The synthesis of α,β-difluoroacrylic acid (FHC═CF−CO2H, DiFAA) and its radical copolymerization with vinylidene fluoride (CH2═CF2, VDF) are presented. First, DiFAA was synthesized in three steps from the radical addition of methanol onto 1,2-dichloro-1,2-difluoroethylene leading to HCFClCFClCH2OH in 78% yield. Then, oxidation of the hydroxymethyl end-group followed by zinc-mediated dehalogenation of 2,3-dichloro-2,3-difluoropropanoic acid led to (Z) isomer of DiFAA in 29% overall yield. The homopolymerization of DiFAA was successfully achieved by radical polymerization initiated by tert-butylperoxypivalate (TBPPi) at 74 °C in 32% yield. Its radical copolymerization with VDF was carried out for the first time and at various compositions leading to functional poly(VDF). The resulting poly(VDF-co-DiFAA) copolymers, characterized by 1H and 19F NMR spectroscopies, exhibited a statistic microstructure. The kinetics of this radical copolymerization led to the assessment of the reactivity ratios (rDiFAA = 0.86 an...

Dielectric properties of block copolymers based on vinylidene fluoride and cyano comonomers

The syntheses of poly(vinylidene fluoride)- b-poly(AN, MAN, VCN) (PVDF- b-PM CN) block copolymers, using the iodine transfer polymerization (ITP) of acrylonitrile (AN), methacrylonitrile (MAN) and vinylidene cyanide (VCN), in the presence of PVDF-I, are presented. In a first step, the ITP of vinylidene fluoride (or 1,1-difluoroethylene, VDF) with C 6F 13I initiated by tert-butyl peroxypivalate is achieved. This ITP led to two different isomeric oligomers (PVDF-I) bearing either CH 2I or CF 2I end-groups. Second step, those fluorinated blocks were used latter as macromolecular chain transfer agents to achieve the ITP with cyanide monomers (M CN). The characterization of synthesized samples by 19F and 1H NMR spectroscopy allowed determining the average degree of polymerization. These block copolymers were characterized by SEC chromatography (4160–51100 g/mol) and by wide angle X-ray diffraction. Their thermal stabilities were studied using thermogravimetric analysis (TGA). The melting and glass transition temperatures as well as the degree of crystallinity were characterized by means of DSC. The influence of the copolymer compositions on dielectric properties has also been investigated. Dielectric analyses show several relaxations processes associated with long-range molecular motions, which are associated to the glass transition temperatures of both blocks (PVDF block and poly(cyano monomer blocks)). These behaviors are discussed in terms of dielectric proprieties as a function of molecular composition and mobility.

Synthesis and characterization of fluorinated PEO- b-PDMS- b-fluorinated PEO by free radical addition

Fluorinated poly(ethylene oxide) propyl- b-polydimethylsiloxane- b-propyl fluorinated poly(ethylene oxide) (FPEO- b-PDMS- b-FPEO) was synthesized by a free radical addition of carbon–hydrogen of polyether segments of poly(ethylene oxide) propyl- b-polydimethylsiloxane- b-propyl poly(ethylene oxide) (PEO- b-PDMS- b-PEO) to hexafluoropropylene (HFP) using tert-butyl peroxypivalate as an initiator. In order to reduce the possibility of side reaction, the protection and deprotection via silylation were used for the end-hydroxyls in PEO- b-PDMS- b-PEO chain. The structure of Intermediates and FPEO- b-PDMS- b-FPEO was confirmed by means of Fourier transform infrared and 1H NMR spectroscopy. The effects of amount of initiator, reaction temperature and time on free radical addition were investigated in detail.

Correlation of Free Radical Copolymerization Behavior and Copolymer Properties with the Strength of π−π Stacking Interactions between Aromatic Fluorocarbons and Aromatic Hydrocarbons: Copolymerization of Styrene and Fluorinated Styrenes at the Two Extreme Levels of Fluorination

In order to determine if the alternating tendency of styrene with fluorinated styrenes in free radical copolymerizations correlates with the strength and/or extent of π-π stacking interactions between aromatic fluorocarbons and aromatic hydrocarbons, styrene (St) was copolymerized with 2,3,4,5,6-pentafluorostyrene (PFS) and 4-fluorostyrene (4FS) under a variety of conditions. For the copolymerization of styrene with PFS at 25 °C, r St r FS = 0.048 and 0.069 in bulk and toluene, respectively, using tert-butylperoxy pivalate as the initiator. For the copolymerization of styrene with PFS at 70 °C using benzoyl peroxide as the initiator, r St r FS = 0.17 in bulk and r St r FS = 0.14 in toluene. For the copolymerization of styrene with 4FS, r St r FS = 0.69 at 25 °C under redox conditions and r St r FS = 0.62 at 70 °C in bulk. As confirmed by 1 H, 13 C, and 19 F one-dimensional NMR and 1 H- 13 C heteronuclear single quantum coherence and 1 H- 1 H nuclear Overhauser effect two-dimensional NMR spectroscopy results, St and 4FS tend to form random copolymers whereas the St-PFS copolymers tend to alternate with the alternating tendency increasing with decreasing temperature. The glass-transition temperatures determined by differential scanning calorimetry of the St-PFS copolymers are elevated relative to their mole-average values, whereas those of the corresponding homopolymer blends and the St-4FS copolymers occur at mole-average values. The water and ethylene glycol contact angles of both the St-PFS and St-4FS copolymer films occur at their mole-average values.

First MALDI-TOF Mass Spectrometry of Vinylidene Fluoride Telomers Endowed with Low Defect Chaining

The radical telomerization of vinylidene fluoride (or 1,1-difluoroethylene, VDF) with iodotrifluoromethane initiated by tert-butyl peroxypivalate is presented. The VDF telomers obtained were characterized by 1H and 19F NMR spectroscopy and by matrix-assisted laser desorption−ionization time-of-flight mass spectrometry (MALDI TOF MS) that revealed low polydispersity indexes showing a pseudo-living character of this reaction regarded as an iodine transfer polymerization process. CF3 and CF2I end groups appear as suitable labels in the 19F NMR spectra to assess the number-average molar masses of these VDF telomers (M̄n). Both these techniques showed a good agreement in terms of degree of telomerization, and the first examples of MALDI−TOF mass spectra of fluorotelomers are presented. Interestingly, all telomers obtained exhibit the structure CF3CH2CF2(VDF)nI, showing that (i) the trifluoromethyl radical preferentially attacked the methylene site of VDF with a high regioselectivity; (ii) the only transfer reaction arose from that to the CF3I and not from the monomer, the initiator, the solvent, or the polymer; and (iii) a very low defect of VDF chaining (0.73% regarded as the lowest one noted in the literature) was observed.

Initiation of free‐radical polymerization by peroxypivalates studied by electrospray ionization mass spectrometry

AbstractInitiation by tert‐butyl peroxypivalate (TBPP), tert‐amyl peroxypivalate (TAPP), 1,1,3,3‐tetramethylbutyl peroxypivalate (TMBPP), or 1,1,2,2‐tetramethylpropyl peroxypivalate (TMPPP) of radical polymerization of methyl methacrylate in toluene solution at 90 °C was studied via polymer end‐group analysis using electrospray ionization mass spectrometry (ESI‐MS). Conclusive peak assignments allowed for measuring the type and concentration of the fragments that actually initiate macromolecular growth after thermal decomposition of these peroxypivalates. It was found that the pivaloyloxy radical moiety undergoes instantaneous decarboxylation to yield an initiating tert‐butyl radical. The alkoxy radical moiety, on the other hand, may generate, via β‐scission reaction, different types of carbon‐centered radicals (together with a ketone) or may undergo a 1,5‐H‐shift reaction, by which reaction an oxygen‐centered radical is transformed into a carbon‐centered hydroxy radical. This hydrogen shift reaction was found in case of TMBPP. Surprisingly, no evidence for initiating alkoxy radicals could be found, not even in case of initiation by TBPP, where the intermediate tert‐butoxy radical undergoes a rapid chain‐transfer reaction with the solvent toluene. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4266–4275, 2004

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group 13. Copolymerization of vinylidene fluoride with 2-benzoyloxypentafluoropropene

The synthesis of 2-benzoyloxypentafluoropropene (BPFP) and its radical copolymerization with vinylidene fluoride (VDF), initiated by tert-butyl peroxypivalate is presented. In a first step, the preparation of two monomers [F 2CC(CF 3)OCOR were R stands for CH 3 or C 6H 5] was attempted. In contrast to the acetoxy derivative that could not be isolated, the benzoyl monomer was purified and then copolymerized with VDF. A series of 11 copolymerization reactions was achieved starting from initial [VDF] 0/([BPFP] 0+[VDF] 0) molar ratios ranging from 19 to 99 mol%. The molar compositions of the obtained copolymers were assessed by means of 19F nuclear magnetic resonance spectroscopy. From the Tidwell and Mortimer method, this kinetics of copolymerization led to the determination of the reactivity ratios, r i , of both comonomers ( r VDF=0.77±0.40 and r BPFP=0.11±0.32). Hence, the Alfrey and Price equation enabled one to assess the Q and e parameters of BPFP as follows: 0.019 (from Q VDF=0.008), 0.043 (from Q VDF=0.015) or 0.182 (from Q VDF=0.036) and 1.97 (vs e VDF=0.40), 2.07 (vs e VDF=0.50) or 2.77 (vs e VDF=1.20), respectively. These Q– e parameters and r i were compared to those of other fluoroalkenes and are discussed.

Radical Homopolymerization of Vinylidene Fluoride Initiated by tert-Butyl Peroxypivalate. Investigation of the Microstructure by 19F and 1H NMR Spectroscopies and Mechanisms

The radical polymerization in solution of vinylidene fluoride (VDF) initiated by different peroxides (tert-butyl peroxide and tert-butyl peroxypivalate) and by azo-tert-butane is presented. Various reaction temperatures and times and solvents were chosen to monitor the polymerization in terms of initiating radical generated from these initiators and transferring agents. Homopolymers thus obtained were characterized by 19F and 1H NMR spectroscopies. Different VDF telomers were synthesized (e.g., C4F9(CH2CF2)3H, C6F13CH2CF2CH2CH3, and CH3CF2(CH2CH2)2I) as models to explain the microstructure of these PVDFs. They enable one to identify without any ambiguity most different signals observed in 1H and 19F NMR spectra of PVDFs. From those assignments, an overall reactional mechanism was proposed that allows one to explain each step of polymerization of VDF. In particular, an interpretation of the polymer microstructures and of end groups arising from the radical initiator and from eventual transfers is suggested.

Initiator efficiency of peroxides in high-pressure ethene polymerization

The initiator efficiency of three organic peroxides, tert-butyl peroxypivalate (TBPP), tert-butylperoxy-2-ethylhexanoate (TBPEH), and di-tert-butyl peroxide (DTBP), has been measured in a stirred tank reactor (CSTR) which is part of a continuously operated miniplant device. The experiments were carried out at 2 000 bar and temperatures between 150 and 250 °C. Initiator efficiency f is defined as the fraction of primary (initiator-derived) free-radical species that add to monomer molecules. The reported data refer to ideal CSTR mixing conditions. The analysis of f is based on results of separate measurements of (i) rate coefficients of peroxide decomposition carried out in dilute solution of heptane and of (ii) ethene propagation and termination rate coefficients from laser single-pulse experiments. The novel quantity “reduced peroxide-induced monomer conversion” defined as the amount of monomer polymerized per square root of the amount of decomposed initiator turns out to be very suitable for deducing initiator efficiency. At the low and moderate ethene conversions, up to 10%, which were applied in the present study, f appears to be independent of temperature. The values of f obtained for DTBP, TBPEH, and TBPP are close to 1.0, 0.64, and 0.42, respectively. The relative low efficiency in TBPP polymerization is primarily assigned to in-cage cross-disproportionation of the tert-butoxy radical with the tert-butyl radical that is instantaneously produced, together with carbon dioxide, during TBPP decomposition. The primary fragments from DTBP decomposition cannot undergo cross-disproportionation, as hydrogen atoms in β-position to the oxygen-centered free-radical site are not available. Schematic view of the continuously operated miniplant device for measuring peroxide-induced ethene conversion in a stirred tank reactor (CSTR) suitable for operation up to 3 000 bar and 300 °C. Polyethylene (PE) is quantitatively collected during pre-selected reaction time intervals. For details see text.

Synthesis and copolymerization of vinylidene fluoride (VDF) with Trifluorovinyl Monomers, 11

The radical telomerization of vinylidene fluoride with 1-chloro-1,2-dibromotrifluoroethane is presented. This dibrominated transfer agent was produced readily from the addition of bromine to chlorotrifluoroethylene in high yields. Four different ways of initiation (thermal, photochemical, or in the presence of redox catalysts or radical initiators) were used in order to obtain optimized yields and degrees of telomerization. Interestingly, the thermal process carried out at 210°C led to fair to good yields in contrast to photochemically induced reaction or that catalyzed by redox systems (this latter reaction produced the monoadduct only). When radical initiators were used, tert-butyl peroxypivalate was the most efficient one, despite the lower reaction temperature. 1 H and 19 F NMR spectra enabled the microstructure of VDF telomers to be described and to determine the cumulative average degrees of telomerization (DP n ). Similarly, gas chromatography, able to detect even the ninth-order adduct, was also useful to assess the DP n . The kinetics of telomerization of this reaction allowed the determination of the first three order transfer constants (C T i ) and led to C T ∞ = 1.3 at 75 °C.

A Novel Organic Peroxyester as an Exclusive Source of tert-Butyl Radicals

Abstract A novel peroxyester, 1,1,2,2-tetramethylpropyl peroxypivalate 1b, has been synthesized and thermolyzed in cumene. The kinetic data show that the decomposition rate constant of 1b is about three times higher than that of tert-butyl peroxypivalate. The radical trapping technique employing 1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yloxyl has been used to study the decomposition mechanism of 1b. The results show that the thermolysis of 1b in cumene generates tert-butyl radicals exclusively.

Initiation Mechanisms for Radical Polymerization of Methyl Methacrylate with tert-Butyl Peroxypivalate

The reaction of tert-butyl peroxypivalate (2) with methyl methacrylate (3) has been studied by the radical trapping technique employing 1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yloxyl (1) as a scavenger. Thermolysis of 2 generated tert-butoxyl, tert-butyl, and methyl radicals in the ratios of 48:50:2 at 60 °C in 3. Both alkyl radicals underwent selective tail addition to 3. tert-Butyl radicals reacted about twice as fast as methyl radicals with 3. The absolute rate constant for addition of tert-butyl radicals to 3 was estimated to be 2.3 × 106 M-1 s-1 at 60 °C. The overall ratio of addition to H abstraction in the reaction of 2 with 3 was 5:1.