Production of poly(β-hydroxyalkanoates) with β-substituents containing terminal ester groups by Pseudomonas oleovorans

Pseudomonas oleovorans was grown separately on the methyl, ethyl and tert-butyl esters of octanoic, nonanoic and decanoic acid in attempts to obtain poly(β-hydroxyalkanoates), PHAs, with ester groups at the terminal position of the β-substituent. The growth rate increased from methyl to tert-butyl esters, but the rate for the slowest growing substrates, the methyl esters, could be accelerated by using special feeding techniques, either by prefeeding with sodium acetate or by cofeeding with a good growth and polymer producing substrate, sodium octanoate. For the ethyl esters the prefeeding technique had minimal success, but a considerable increase of the growth rate was achieved by starting the bacterial growth with a pre-culture that was grown on the substrate under investigation. Tert-butyl nonanoate as the substrate gave the most rapid growth, but the growth rate was not influenced by special feeding techniques. All of these substrates formed copolymers which contained up to eight different repeating units and some had terminal ester groups on alkane side chains of varying lengths. The use of methyl esters as substrates resulted in the incorporation of a reasonably high degree of pendant methyl ester groups in the polymer produced, and the amount of repeating units carrying pendant ester groups dependend directly on the oxygen supply available to the bacterial culture. The fermentation of substrates with ethyl ester groups resulted in the formation of copolymers containing either unsubstituted units or units containing either ethyl or methyl ester groups, or both. The reason for this unexpected behavior was not clarified. The large tert-butyl ester group was not maintained as a substituent group in the polymer, but instead, growth on this substrate always resulted in producing polymers consisting of the unsubstituted repeating units expected from the corresponding carboxylic acid alone.     

tert-Butyl peresters as initiators in vinyl polymerizations. I.

Peresters dissociate thermally to alkoxy and acyloxy radicals. The acyloxy radical may dissociate further into an aryl radical and carbon dioxide. Alternatively they may break into these products in a single stage reaction. The decomposition of tert-butyl perbenzoate has been studied and it has been shown that the primary products of the dissociation of this ester are alkoxy and acyloxy radicals. The polymerization of styrene, using tert-butyl perbenzoate, tert-butyl percinnamate and tert-butyl percrotonate has been studied at 120 ± 1°C. It has been shown that the rate of polymerization is proportional to the square root of the initiator concentration and the 3/2 power of the monomer concentration.     

Study of the propagation centre in the anionic polymerization of (meth)acrylic monomers, 5. Nuclear magnetic resonance study of the model dimer in tetrahydrofuran

Di-tert-butyl 2-lithio-2,4,4-trimethylglutarate ( 1 ) as a model of the living dimer of tert-butyl methacrylate was studied in deuterated tetrahydrofuran (THF-d₈) solution by ⁶Li, ⁷Li, ¹H and ¹³C NMR. In agreement with earlier observations from infrared spectroscopy and with quantum chemical ab initio and semiempirical self-consistent field calculations, 1 is shown to have a strong tendency to an intramolecular coordination of Li to the penultimate ester carbonyl group. The competing linear form of 1 (with uncoordinated penultimate ester group) is shown to exist due to its stabilization by self-aggregation to form a dimer of 1 . In contrast to the monomeric form of 1 , the dimer does not bind THF into a specific solvate. Given the entropy-driven solvation at low temperatures, the occurrence of the dimeric aggregate is enhanced by higher temperature and concentration of 1 . Both the cyclic and linear form of 1 are shown to exist in at least two different conformers and various solvation states. Their mutual exchange is several orders of magnitude slower than the anionic propagation reaction of tert-butyl methacrylate.     

Reduction of the cationic growing center of polyisobutylene by activated magnesium. Block copolymerization of isobutylene with tert-butyl methacrylate

Transformation of the tert-chlorine end group of poly(isobutylene) into a terminal Grignard group was studied with the motivation of producing a PIB macroanion. The reduction of the terminal tert-chlorine group was completed within 30 min at room temperature by using activated magnesium (Mg^*) prepared by the reaction of MgCl₂ with lithium naphthalenide. The efficiency of the transformation was 28%, which was determined by end-group analysis of the polymer obtained after quenching the reduction with methyl 2-phenylacetate in the presence of CeCl₃. The terminal carbanion prepared by this method initiated the polymerization of tert-butyl methacrylate (TBMA) to give a block copolymer consisting of an anionically and a cationically polymerizable monomer.     

Endgroup-functionalized polytetrahydrofurans by polymerization with functional triflate esters, 1. PolyTHF-macromonomers

Functional esters of trifluoromethanesulfonic acid (triflate esters) have been synthesized by reaction of functional alcohols (allyl alcohol, 2-hydroxyethyl acrylate (HEA) and methacrylate (HEMA), 4-hydroxybutyl acrylate (HBA)) with triflic anhydride in the presence of 2,6-di-tert-butylpyridine. These esters were used in situ as initiators for the polymerization of tetrahydrofuran (THF), with the purpose to synthesize endgroup-functionalized polyTHF's. The method was first tested with the system butanol/triflic anhydride. With this combination, quantitative formation of the ester and, subsequently, controlled polymerization of THF was realized. Similar results were obtained with the system allyl alcohol/triflic anhydride. With 2-hydroxyethyl acrylate (HEA) and 2-hydroxyethyl methacrylate (HEMA), the synthesis of the triflate ester was accompanied by the formation of substantial amounts of ether formed by reaction of the triflate ester with a second molecule of alcohol. This was attributed to an enhanced reactivity of the triflate ester due to nucleophilic assistance by the carbonyl group in γ-position. This assistance is not possible with 4-hydroxybutyl acrylate (HBA) and with this alcohol, the formation of the ester was almost quantitative. The synthesis of polyTHF acrylate macromonomer was successful with the latter system.     

Copolymers from tert‐Butyl Methacrylate with Trimethylsilyl Methacrylate or Methacrylic Acid: Models for Resist Polymers

Free radical copolymerisation of tert‐butyl methacrylate ( 1 ) with trimethylsilyl methacrylate ( 2 ) and methacrylic acid ( 3 ) has been investigated. Reactivity ratios for methacrylic acid and tert‐butyl methacrylate indicate an azeotropic copolymerisation (r ₁ = 0.476 ± 0.103; r ₃ = 0.300 ± 0.032), whereas the two esters show preferential incorporation of 2 (r ₁ = 0.170 ± 0.050; r ₂ = 1.170 ± 0.124). Thermal cis‐elimination of isobutylene from the tert‐butyl ester and subsequent formation of six‐membered cyclic anhydride moieties has been studied. For poly(methacrylic acid‐co‐tert‐butyl methacrylate) thermogravimetry could be used to determine copolymer composition. Solvolytic desilylation of the trimethylsilyl ester groups has been investigated as an alternative route to poly(methacrylic acid‐co‐tert‐butyl methacrylate). The tert‐butyl ester is not affected under the conditions of desilylation. Sequence distribution of both copolymers has been calculated using the method introduced by Bruns and Motoc.

Copolymer composition diagram for tert‐butyl methacrylate/methacrylic acid.     

Synthesis and free radical ring-opening polymerization of 2-methylene-4-phenyl-1,3-dioxolane

The cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane ( 3 ), was shown to undergo free radical ring-opening polymerization to produce the polyester, poly[γ-(β-phenyl)butyrolactone]. The monomer 3 was synthesized by an acetal exchange reaction of chloroacetaldehyde dimethyl acetal with styrene glycol in an 87% yield followed by dehydrochlorination of the resulting cis and trans-2-chloromethyl-4-phenyl-1,3-dioxolane ( 2 ) with potassium tert-butoxide in tert-butyl alcohol in a 70% yield. 3 was shown to undergo essentially quantitative free radical ring-opening at all temperatures from 60–150°C and also nearly complete regioselective ring-opening with cleavage to give the more highly stable secondary benzyl free radical. Even in free radical copolymerization with styrene, methyl methacrylate, vinyl acetate, or 4-vinylpyridine, 3 gives essentially complete ring opening to introduce an ester groups into the backbone of the addition copolymer. The structures of the polymers were established by elemental analysis and ¹H and ¹³C NMR spectroscopy.     

Stabile polysauerstoff-radikale. I. Synthese von polymerisationsfähigen monomeren mit sterisch behinderter freier oder geschützter phenolischer hydroxylgruppe

New monomers with sterically hindered free or blocked phenolic hydroxyl groups were used as starting compounds for the preparation of stable oxygen polyradicals. In this paper the synthesis of these monomers is described: 2,6-Di-(tert-butyl)-4-vinylphenol was obtained by decarboxylation of 3-[3,5-di-(tert-butyl)-4-hydroxyphenyl]acrylic acid in yields of 80–;90%. 2,6-Di-(tert-butyl)-4-isopropenylphenol was prepared from 3,5-di-(tert-butyl)-4-hydroxyphenyl methyl ketone and methyl iodide by a GRIGNARD reaction followed by the dehydration of 2-[3,5-di-(tert-butyl)-4-hydroxyphenyl]-2-propanol. 2,6-Di-(tert-butyl)-4-isopropenylphenyl methyl ether was obtained with 64% yield from 3,5-di-(tert-butyl)-4-methoxybenzonitrile by two consecutive GRIGNARD reactions with methyl iodide via the unknown compounds 3,5-di-(tert-butyl)-4-methoxyphenyl methyl ketone and 2-[3,5-di-(tert-butyl)-4-methoxyphenyl]-2-propanol, followed by dehydration of the tertiary alcohol with 89% phosphoric acid.     

ABC triblock polyampholytes containing a neutral hydrophobic block,a polyacid and a polybase

Well defined ABC triblock copolymers of polystyrene-block-poly(2-vinylpyridine)-block-poly(tert-butyl methacrylate) and polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) were synthesized by sequential living anionic polymerization in tetrahydrofuran. Triblock copolymers with narrow molecular weight distribution were obtained. Hydrolysis of the poly(tert-butyl methacrylate) block yields polystyrene-block-polyvinylpyridine-block-poly(methacrylic acid) which demonstrates pH-dependent solution properties. Interpolymer complexation of the polyvinylpyridine and poly(methacrylic acid) blocks in the micellar solution is studied in dependence of the pH in solution by potentiometric, conductometric and turbidimetric titration, and in bulk by FTIR spectroscopy.     

Synthesis of polyamic acid di-tert-butyl esters by direct polycondensation of di-tert-butyl esters of tetracarboxylic acids with diamines using diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate

The direct polycondensation using the activating agent diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate ( 1 ) was successfully applied to the synthesis of polyamic acid tert-butyl esters, which readily undergo A_AL 1 type acid-catalyzed deesterification. Polycondensations of di-tert-butyl esters of tetracarboxylic acids with diamines were conducted in N-methyl-2-pyrrolidone in the presence of triethylamine at room temperature, producing poly(amide-ester)s with inherent viscosities up to 1,1 dL · g^?1. The effects of various factors, such as solvent, amount of solvent, and amount of the activating agent, were studied. The poly(amide-ester)s are readily soluble in dipolar aprotic solvents and can be cast into uniform films from their solutions. Thermogravimetry of the polymers showed that the deesterification and imidization occur around 150–200°C, giving polyimides.     

Reactive microgels by the self-emulsifying copolymerization of unsaturated polyester resins with acrylic and methacrylic esters

The self-emulsifying copolymerization of unsaturated polyesters (UP) with various acrylic and methacrylic esters was studied. The structure of comonomers significantly influences the character of microgels obtained. Among these monomers the copolymerization of UP with methyl methacrylate (MMA) was investigated in detail in order to make clear the behavior of this polymerization as compared with that of styrene. The water/monomer and UP/MMA ratios were found to be the most important factors controlling the molecular weight and solution viscosity of the microgels. The relationship between M?_w and intrinsic viscosity of microgels suggests that the microgels from MMA have less compact structure than those from styrene.     

Mechanisms and kinetics of the anionic polymerization of acrylates, 1. Oligomerization of tert-butyl acrylate and characterization of products

The anionic polymerization of tert-butyl acylate (tBuA) initiated by tert-butyl α-lithioisobutyrate was investigated in THF at 25°C. The individual oligomers were isolated and characterized by UV, IR and NMR spectroscopy. The distribution of products was determined in the range of reaction times 0,02 s ≤ t ≤ 1800 s. The oligomerization is extremely fast. Even after 0,02 s at -30°C, no residual monomer could be detected. After short reaction times the reaction mixture almost exclusively consists of linear oligomers of tBuA. This indicates that there is no termination reaction by Claisen condensation during polymerization. Nevertheless, the molecular weight distribution is rather broad (M?_w/M?_n = 2,1₅). The very large amount of dimer observed is an indication of its low reactivity. A two-state mechanism is proposed to account for the high polydispersity. Only after longer reaction times side products are formed by Claisen condensation (“back-bitting”). The termination product of the trimer is an enolized cyclic β-ketoester.     

Reactivity of polystyrene and model compounds toward tert-butoxy radicals

tert-Butoxy radicals were generated by decomposing di-tert-butyl hyponitrite. The relative reactivities of substrates were measured from the ratio of tert-butanol and acetone formed. Polystyrene was found to be less reactive than model compounds. Activation parameters for the hydrogen abstraction reaction for cumene, 3-phenylpentane, and 2,4-diphenylpentane are reported and show small differences for the enthalpy of activation; large negative values for the entropy of activation demonstrate the importance of steric hindrance in the hydrogen abstracting step. 2,3-Diphenylbutane as model compound for head to head links in polystyrene exhibits low reactivity, whereas 2,5-diphenylhexane, a model for tail to tail links, is more reactive than the dimer head to tail model. Still more reactive is 2,4-diphenyl-2-pentene as model for an unsaturated unit in polystyrene.     

Influence of the crown ether concentration and the addition of tert-butyl alcohol on anionic polymerization of (butoxymethyl)oxirane initiated by potassium tert-butoxide

The influence of the crown ether concentration on the reaction rate constants and the equilibrium constant in anionic (butoxymethyl)oxirane polymerization was studied. Polymerizations of (phenoxymethyl)oxirane and (2-(9-carbazoyl)ethoxymethyl)oxirane were carried out for the sake of comparison. The observed changes caused by the addition of the crown ether can be related to both the structure of its complex with the counter-ion and the structure of the monomer molecule. It was also revealed the tert-butyl alcohol reduces the concentration of active centers and the molecular weight of the polymers.     

Ceric ion consumption in graft copolymerization of methacrylonitrile/methacrylate mixtures onto amylomaize

A study on the Ce(IV) consumption in the graft copolymerization of methacrylonitrile/n-alkyl methacrylate mixtures methyl, ethyl and butyl methacrylate/methacrylonitrile (MMA/MAN, EMA/MAN and BMA/MAN) was carried out. Ce(IV) consumption increased with increasing mole fraction of the methacrylate in the monomer feed and with increasing the n-alkyl group length of the methacrylate, but in no case the consumption was total. The molecular weight distribution of the copolymers was obtained through gel-permeation chromatography. For all systems investigated, both number-average molecular weight (M _n) and weight-average molecular weight (M _w) increased with increasing methacrylate concentration in the monomer feed. The ratios M _w/M _n increased in the following order: MMA/MAN < EMA/MAN < BMA/MAN. For the MAN/MMA system, the number of grafted chains (in mmol) increased as the methyl methacrylate content increased in the monomer feed, and for the MAN/EMA and MAN/BMA systems, this parameter presented a maximum value. The number of D -anhydroglucose units per grafted chain (frequency) decreased with increasing methacrylate concentration in monomer feed for the MAN/MMA system, and this parameter reached a minimum value at a methacrylate mole fraction of 0,5 for the other two systems.     

Mechanisms and kinetics of the anionic polymerization of acrylates, 3. Effect of lithium chloride and lithium tert-butoxide on the oligomerization of tert-butyl acrylate

The influence of lithium tert-butoxide (tBuOLi) and of lithium chloride on the oligomerization of tert-butyl acrylate (tBuA) initiated by tert-butyl α-lithioisobutyrate (tBiB-Li) was investigated. These additives affect both the kinetics and the product distribution. Whereas the addition of LiCl leads to a narrower molecular-weight distribution (MWD) the presence of tBuOLi induces broader MWD's, characterized by a very high fraction of the dimer. Both additives decrease the rates of propagation to different degrees. These effects are discussed on the basis of the formation of aggregates and adducts, the lithiated dimer having a higher tendency to form aggregates than the other oligomers. The stability of the growth centres in this oligomerization is increased in the presence of these additives, tBuOLi exhibiting a much stronger effect than LiCl. The interaction of the lithiated dimer with the additives could not be demonstrated in the IR spectra of these mixtures.     

Reaction modes and polymerization of crotonic esters with lithium aluminum hydride

The reaction products of lithium aluminum hydride with crotonic esters under polymerization conditions were analyzed by gas chromatography. The ratios of carbon-carbon double bond- to carbonyl-addition of the hydride ion toward methyl, iso-propyl, iso-butyl and sec-butyl crotonates are determined as 3:1, 20:1, 9:1, and 40:1, respectively. The intermediate double bond addition product was confirmed to be a precursor of the polymerization. The precursors undergo successive carbonyl-addition onto monomer, terminating the propagation rapidly in the reactions with methyl and isobutyl esters; in case of iso-propyl and sec-butyl esters double bond additions yielded high polymers. The reaction product of methyl crotonate and lithium aluminum hydride showed good catalytic activity for polymerization of crotonates.     

Studies on polymerizations initiated by syncatalytic systems based on aluminium organic compounds, 6. Comparison with isobutene polymerizations initiated by ethylaluminium dichloride or aluminium trichloride

The results of previous studies carried out on the polymerization of isobutene initiated by diethylaluminium halides plus halogens are compared with results obtained with other syncatalytic systems such as diethylaluminium chloride (or triethylaluminium) plus hydrochloric acid (or tert-butyl chloride), as well as with results obtained with aluminium compounds such as ethylaluminium dichloride or aluminium trichloride which do not require co-initiators to initiate the polymerization of isobutene. The kinetic data indicate clearly that the polymerization of isobutene initiated by syncatalytic systems is characterized by a relatively slow initiation and by the absence of important termination reactions and of transfer with monomer. In contrast to this, the polymerizations initiated by strong Lewis acids such as ethylaluminium dichloride or aluminium trichloride show a much faster initiation and stop at incomplete conversion which indicates that at least one efficient termination reaction is operative. It is also demonstrated that this termination reaction produces at least one substance which acts as a co-initiator for the isobutene polymerization initiated by diethylaluminium halides or triethylaluminium.     

The microtacticity of poly(acrylic esters)

Several acrylic esters were polymerized with radical and anionic initiators and the stereoregularity of the polymers was determined. The radical polymerization of tert-butyl acrylate gave syndiotactic-rich polymers at low temperatures as did isopropyl and trimethylsilyl acrylates. A radically obtained polymer of triphenylmethyl acrylate was atactic in contrast to poly(triphenylmethyl methacrylate). In the anionic polymerization with phenylmagnesium bromide or butyllithium as catalyst, the stereoregularity of the polymers was governed by the coordination of the catalyst which depends on the polarity and bulkiness of ester groups, the polarity of solvents, and the temperature in the polymerization.     

Kinetics of group transfer polymerization of tert-butyl methacrylate in tetrahydrofuran

The reaction kinetics for the group transfer polymerization (GTP) of tert-butyl methacrylate (TBMA) using a silyl ketene acetal initiator and a nucleophilic catalyst are investigated. The reaction is shown to be of first order in both monomer and catalyst concentrations. The “livingness” of this system appears to be influenced by the reaction temperature. At temperatures above ?20°C, deactivation is observed, with its severity increasing with increasing temperature. This deactivation is attributed to a depletion of catalyst by side reactions. It was demonstrated that reactivation is made possible by the addition of more catalyst. This result is in contrast to the anionic polymerization of TBMA, where no deactivation was observed even at ambient temperature. At temperatures below ?20°C no deactivation is observed; however, at these temperatures, the reactions manifest induction periods with lengths increasing with decreasing temperature. The rate constants are lower than those for the GTP of methyl methacrylate (MMA) by a factor of 1,5 to 2. The following Arrhenius parameters were obtained for the propagation rate constants: activation energy, E_a = (19,₁ ± 3) kJ/mol, preexponential factor, log₁₀ A = (7,0₅ ± 0,3). These values are comparable with those obtained for MMA. The molecular weight distributions are similar to those obtained in the GTP of MMA, i.e. the ratio of weight-to number-average molecular weights is rather high for low monomer conversions and narrows to M?_w/M?_n ≥ 1,3 for full conversion. This is attributed to the rates of the catalyst exchange equilibrium.