Duygu Avci

Synthesis and photopolymerization kinetics of new flexible diacrylate and dimethacrylate crosslinkers based on C18 diacid

Abstract A series of new di(meth)acrylate monomers was synthesized from the reactions of methyl α-hydroxymethylacrylate (MHMA), ethyl α-hydroxymethylacrylate (EHMA), hydroxyethyl acrylate (HEA) and hydroxyethylmethacrylate (HEMA) with α,ω-C18 diacid chloride. The photopolymerization behavior and reaction kinetics of the synthesized monomers were investigated using photoinitiation with differential scanning calorimetry. The polymerization rates, conversions and kinetic constants for propagation and termination were determined for each of the monomers. The maximum rate of polymerizations of the diacrylate monomers was higher than that of the dimethacrylate monomers and followed the order: HDDA (1,6-hexanediol diacrylate)>HEA-C18>EHMA-C18∼HEMA-C18>MHMA-C18. The total conversions obtained were 78, 75, 72, 64 and 69% for MHMA-C18, EHMA-C18, HEMA-C18, HEA-C18 and HDDA, respectively, indicating comparable or higher conversions for methacrylates despite their lower rates of polymerization. Propagation and termination mechanisms of the monomers were investigated by plotting propagation and termination rate constants as a function of conversion.

Synthesis and antibacterial activities of new quaternary ammonium monomers

New monomers and polymers with amine and quaternary ammonium groups on the side chain were synthesized. The first series of monomers were the derivatives of 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM). Hydroxylated secondary and tertiary amine derivatives were prepared by reaction of AHM with various amines. One of the amine monomers was quaternized with bromohexane to give a quaternary ammonium monomer. A second series of amine and quaternary ammonium monomers were based on acrylamide and methacrylamide derivatives. New acrylamide/methacrylamide monomers with tertiary amine groups were synthesized and quaternized with various alkyl halides. All monomers were homo-polymerized and co-polymerized with 2-hydroxyethylmethacrylate (HEMA). The synthesized monomers and polymers were tested for antibacterial activities against Staphylococcus aureus and Escherichia coli bacteria. Amine monomers, their homo-polymers and co-polymers did not show any antibacterial activities. It was also found that the antibacterial activity of the quaternized methacrylamide-3-(aminomethyl) pyridine (METH-PYR) monomers increased as the alkyl chain length on nitrogen increased.

Synthesis and Cyclopolymerization of Novel Allyl-Acrylate Quaternary Ammonium Salts

Novel allyl-acrylate quaternary ammonium salts were synthesized using two different methods. In the first (method 1), N,N-dimethyl-N-2-(ethoxycarbonyl)allyl allylammonium bromide and N,N-dimethyl-N-2-(tert-butoxycarbonyl)allyl allylammonium bromide were formed by reacting tertiary amines with allyl bromide. The second (method 2) involved reacting N,N-dialkyl-N-allylamine with either ethyl α-chloromethyl acrylate (ECMA) or tert-butyl α-bromomethyl acrylate (TBBMA). The monomers obtained with the method 2 were N,N-diethyl-N-2-(ethoxycarbonyl)allyl allylammonium chloride, N,N-diethyl-N-2-(tert-butoxycarbonyl)allyl allylammonium bromide, and N,N-piperidyl-N-2-(ethoxycarbonyl)allyl allylammonium chloride. Higher purity monomers were obtained with the method 2. Solution polymerizations with 2,2′-azobis(2-amidinopropane) dihydrochloride (V-50) in water at 60–70°C gave soluble cyclopolymers which showed polyelectrolyte behavior in pure water. Intrinsic viscosities measured in 0.09M NaCl ranged from 0.45 to 2.45 dL/g. 1H- and 13C-NMR spectra indicated high cyclization efficiencies. The ester groups of the tert-butyl polymer were hydrolyzed completely in acid to give a polymer with zwitterionic character.

Cyclopolymerization of amine-linked diacrylate monomers

New diacrylate monomers for cyclopolymerization were synthesized from the reaction of ethyl α-chloromethylacrylate (ECMA) and t-butyl α-bromomethyl acrylate (TBBr) with aniline, adamantyl amine, t-butyl amine, cyanamide, and 4-tetradecyl aniline in yields of ca. 50–70%. Bulk and solution polymerizations with azobisisobutyronitrile (AIBN) at 60–85°C gave soluble cyclopolymers with Mn and Mw ranging from 10,000–30,000 and 12,000–40,000, respectively. The ECMA–cyanamide derivative only gave crosslinked polymers. 1H and 13C solution NMR indicated high cyclization efficiency (>93%). A prototype NLO polymer was synthesized from the reaction of the TBBr–aniline cyclopolymer with tetracyanoethylene. The p-hydroxyaniline derivative of ECMA was synthesized and used for further derivatizations; for example, the benzoate ester was made and polymerized (Mn = 21,260 and Mw = 40,317). The ester groups of the TBBrndash;aniline polymer were hydrolyzed completely to give a polymer with both acid and base moieties. DSC thermograms showed glass transitions of 132°C for the ECMA–aniline derivative, 192°C for the ECMA–adamantyl derivative, 53°C for the TBBr–tetradecylaniline derivative, and 120° for the ECMA–p-benzoylaniline derivative. The ECMA–t-butyl amine polymer showed no obvious Tg.

Synthesis and Photo-Polymerization of an Aryl Diphosphonic Acid-Containing Dimethacrylate for Dental Materials

A new dental dimethacrylate monomer containing phosphonic acid functionality, 2,5-bis(methacryloyloxy)-1,4-phenylenediphosphonic acid (1), was synthesized by silylation of 2,5-bis(diethoxyphosphoryl)-1,4-phenylene bis(2-methylacrylate) (2) with trimethylsilyl bromide (TMSBr) followed by the hydrolysis of the silyl ester. The monomer was solid and soluble in ethanol and water. The structure of this monomer was characterized by 1H-, 13C-, 31P-NMR and FT-IR spectroscopy. The aqueous solution of 1 is acidic (pH 1.65), so that it is expected to etch enamel and dentin, but is prone to hydrolysis over long storage periods. The co-polymerization behavior of this monomer with 2-hydroxyethyl methacrylate (HEMA) was investigated in water using photodifferantial scanning calorimeter at 40°C with bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO) as photoinitiator. It was observed that the addition of monomer 1 to HEMA slightly decreased both the maximum rate of polymerization and conversion. The thermal solution co-polymerization of this monomer with acrylamide (AAm) and HEMA gave cross-linked polymers, indicating its incorporation into the co-polymers. The interaction of this monomer with hydroxyapatite was observed using FT-IR spectroscopy. This monomer was found to be more suitable for dental composites than dental adhesives.

Novel phosphorus-containing cyclopolymers from ether dimer of tert-butyl α-hydroxymethyl acrylate

A new acrylate monomer with phosphonic acid ester groups was synthesized from the reaction of the acid chloride derivative of the ether dimer of tert-butyl α-(hydroxymethyl) acrylate with diethyl hydroxymethyl phosphonate. Bulk polymerization of this monomer at 75-77°C with 2,2′-azobisisobutyronitrile (AIBN) gave soluble cyclopolymers. The T g value of the cyclopolymer was 44°C, and produced a char yield of 36% at 580°C. The phosphonate monomer was copolymerized with the ether dimer of tert-butyl α-(hydroxymethyl) acrylate in different ratios. The T g of the copolymers decreased with increasing amounts of the phosphonate monomer in the copolymers, with the values of 148, 105 and 93°C for the copolymers containing 10, 30 and 50 mol% phosphonate monomer in feed, respectively. The char residues of the copolymers increased with the incorporation of the phosphonate monomer. The selective hydrolysis of the phosphonate monomer with trimethylsilyl bromide (TMSBr) gave a monomer with two phosphonic acid groups. The polymerization of this monomer at 70-75°C with AIBN was unsuccessful; however, this monomer was copolymerized with the ether dimer of tert-butyl α-(hydroxymethyl) acrylate and its carboxylic acid derivative.

Cyclocopolymerization of allyl‐acrylate quaternary ammonium salts with diallyldimethylammonium chloride

A series of copolymers of N,N-dialkyl-N-2-(methoxycarbonyl)allyl allyl ammonium chloride, N,N-dialkyl-N-2-(ethoxycarbonyl)allyl allyl ammonium chloride, and N,N-dialkyl-N-2-(t-butoxycarbonyl)allyl allyl ammonium bromide with diallyldimethylammonium chloride (DADMAC) were prepared in water at 60 °C with 2,2′-azo-bis(2-amidinopropane)dihydrochloride. A strong effect of ester substituents on cyclopolymerization was observed. The methyl and ethyl ester monomers showed high cyclization efficiencies during homopolymerizations and copolymerizations. Unexpectedly, the t-butyl ester derivatives showed high crosslinking tendencies. Water-soluble copolymers were obtained only with a decrease in the molar fraction of t-butyl ester monomer below 30%. Relative reactivities of the allyl-acrylate monomers in photopolymerizations were compared with the relative reactivity of DADMAC. Allyl-acrylate monomers were much more reactive than DADMAC; the photopolymerization rate decreased in the following order: N,N-morpholine-N-2-(t-butoxycarbonyl)allyl allyl ammonium bromide > N,N-piperidyl-N-2-(t-butoxycarbonyl)allyl allyl ammonium bromide > N,N-dibutyl-N-2-(ethoxycarbonyl)allyl allyl ammonium chloride > N,N-piperidyl-N-2-(ethoxycarbonyl)allyl allyl ammonium chloride ∼ N,N-morpholine-N-2-(ethoxycarbonyl)allyl allyl ammonium chloride ∼ N,N-piperidyl-N-2-(methoxycarbonyl)allyl allyl ammonium chloride > N-methyl-N-butyl-N-2-(ethoxycarbonyl)allyl allyl ammonium chloride. Intrinsic viscosities of the polymers measured in 0.09 M NaCl ranged from 1.06 to 3.20 dL/g. The highest viscosities were obtained for copolymers of the t-butyl ester monomers with piperidine and morpholine substituents. The copolymer of the t-butyl ester with piperidine substituent and DADMAC was hydrolyzed in acid to give a polymer with zwitterionic character.

Cyclopolymerization of cinnamate ester derivatives of alkyl α-(hydroxymethyl) acrylates

SummaryThree new monomers for cyclopolymerization were synthesized using phase transfer catalysis of ethyl α-(chloromethyl) acrylate (ECMA), t-butyl α-(bromomethyl) acrylate (TBBMA) and isobornyl α-(bromomethyl)acrylate (IBBMA) with cinnamic acid sodium salt. Bulk and solution polymerization at 70–80°C using AIBN gave soluble cyclopolymers with Mn=13650 and Mw=36540 for the ethyl ester, Mn=47700 and Mw=86900 for the t-butyl ester and Mn=3500 and Mw=4650 for the isobornyl ester monomer. The ester polymerizabilities decreased with increasing substituent bulkiness. FTIR spectra showed ca 30 to 93% cyclic units depending on the concentration of the monomer used in polymerizations. DSC thermograms showed that alkyl group size had little effect on Tgs, with values of 151°C, 156°C, and 164°C for the ethyl, t-butyl and isobornyl esters, respectively.

Bisphosphonate-functionalized poly(β-amino ester) network polymers

Three novel bisphosphonate-functionalized secondary diamines are synthesized and incorporated into poly(β-amino ester)s (PBAEs) to investigate the effects of bisphosphonates on biodegradation and toxicity of PBAE polymer networks. These three novel amines, BPA1, BPA2, and BPA3, were prepared from the reactions of 1,4-butanediamine, 1,6-hexanediamine, or 4,9-dioxa-1,12-dodecanediamine with tetraethyl vinylidene bisphosphonate, respectively. The PBAE macromers were obtained from the aza-Michael addition reaction of these amines to 1,6-hexane diol diacrylate (HDDA) and poly(ethylene glycol) diacrylate (PEGDA, Mn  = 575) and photopolymerized to produce biodegradable gels. These gels with different chemistries exhibited similar degradation behavior with mass loss of 53-73% within 24 h, indicating that degradation is mostly governed by the bisphosphonate group. Based on the in vitro cytotoxicity evaluation against NIH 3T3 mouse embryonic fibroblast cells, the degradation products do not exhibit significant toxicity in most cases. It was also shown that PBAE macromers can be used as cross-linkers for the synthesis of 2-hydroxyethyl methacrylate hydrogels, conferring small and customizable degradation rates upon them. The materials reported have potential to be used as nontoxic degradable biomaterials.

Polymerization of α-(N-vinylformamidomethyl)acrylates: cyclopolymers from non-symmetric monomers

t-Butyl α-(N-vinylformamidomethyl)acrylate (tBVFA) and ethyl α-(N-vinylformamidomethyl)acrylate (EVFA) were synthesized from t-butyl α-bromomethylacrylate and ethyl α-chloro-methylacrylate, respectively. tBVFA was found to cyclopolymerize at 120°C in DMF, DMSO, and 1,2-dichlorobenzene at solvent: monomer ratios of 10 : 1 vol : wt. Molecular weights for poly(tBVFA) ranged from 10 000 to 13 000 as estimated by size-exclusion chromatography. At lower solvent monomer ratio (1 : 1), and at lower temperature (71°C), crosslinking occurred. EVFA was found to cyclopolymerize, but only in DMF at 122°C and at a 10: 1 solvent: monomer ratio.