Synthesis and photopolymerizations of new hydroxyl-containing dimethacrylate crosslinkers

Two new hydroxyl-containing di(meth)acrylate monomers were synthesized from the reaction of methyl α-chloromethylacrylate (MCMA) and of ethyl α-chloromethylacrylate (ECMA) with glycerol. The monomers were obtained as mixtures of two isomers in different ratios and in combination with the analogous trimethacrylate monomers. Each monomer was isolated by column chromatography. The photopolymerization of these isomer mixtures and the trimethacrylate monomers was investigated individually by photodifferential scanning calorimetry (photoDSC) at room temperature using 2,2′-dimethoxy-2-phenyl-acetophenone (DMPA) as a photoinitiator. The effect of hydrogen bonding on the rates of polymerizations and conversions was examined. The results obtained for the synthesized monomers were compared to the values obtained for commercial monomers. It was observed that the hydroxyl-containing dimethacrylates polymerize much faster and to considerably higher conversion than the trimethacrylate monomers. The maximum rates of polymerization of the hydroxyl-containing monomers were higher than that of the hexanediol dimethacrylate (HDDMA), comparable to glycerol dimethacrylate and lower than hexanediol diacrylate (HDDA) and 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM).     

Spatially resolved studies on the photopolymerization of dimethacrylate monomers

The photopolymerization of four dimethacrylate monomers under different irradiating conditions was followed in situ by ¹H stray-field magnetic resonance imaging (¹H STRAFI-MRI). This technique is capable of discriminating local changes at a spatial resolution of tens of micron and is suitable for studying larger samples than infrared spectroscopy and photocalorimetry. The evolution of proton magnetization with irradiation time and intensity was recorded and correlated with volumetric polymerization shrinkage, extent of reaction and spatially resolved reaction rates.     

环氧丙烯酸酯/乙烯基醚光聚合反应动力学研究

以二缩乙二醇二乙烯基醚 (DVE -3 )为活性稀释剂 ,研究其与环氧丙烯酸酯 (EOA)所组成的光聚合体系在自由基型光引发剂下引发的光聚合反应动力学及其影响因素。DVE -3含量越大 ,EOA/DVE -3体系的转化率越低。体系粘度的提高有利于提高其反应速率。若在环氧丙烯酸酯中引入马来酸酯结构 ,则马来酸酯的含量越大 ,体系的转化率越高 ,马来酸酯结构的引进 ,可以降低体系聚合后残余的双键含量。     

Understanding multivinyl monomer photopolymerization kinetics through modeling and GPC investigation of degradable networks

Multivinyl monomers that react to form highly crosslinked, biodegradable networks are being developed as scaffolds for tissue engineering and vehicles for drug delivery; however, this work demonstrates their usefulness in characterizing better the complexities of the kinetics and structural evolution during crosslinking photopolymerization. The molecular weight distributions (MWDs) of the degradation products of networks formed through the free radical photopolymerization of multivinyl monomers validate a novel kinetic model to test hypotheses as to the important kinetic mechanisms during crosslinking. The kinetic model, in conjunction with the experimental results for the degradable network, provides insight into the fundamental termination mechanisms (i.e. chain length dependent termination (CLDT), chain transfer to either a unimolecular species or polymer, and the accumulation of persistent radicals) that control the MWD of the backbone kinetic chains throughout the polymerization. Specifically, the importance of CLDT during autoacceleration and the impact of light intensity on the MWD of the backbone kinetic chains are presented.     

Synthesis and photopolymerization of novel,highly reactive phosphonated-urea-methacrylates for dental materials

An urea methacrylate (1) and two phosphonated methacrylates (2–3) were synthesized from 2-isocyanatoethyl methacrylate (IEM) and benzyl amine (1), diethyl aminomethylphosphonate (2) and diethyl amino(phenyl)methylphosphonate (3). Their photopolymerization rates are notably higher than commercial monomers, despite the presence of only one double bond. Their polymerization rates follow the order 1 ～ 2 > 3 ～ triethylene glycol dimethacrylate (TEGDMA) > 2-hydroxyethyl methacrylate (HEMA). A tendency toward high crosslinking density during thermal bulk polymerizations, low oxygen sensitivity and high conversions with benzophenone during photopolymerization indicated the importance of hydrogen abstraction/chain transfer reactions. It was found that the addition of the monomers to HEMA significantly increased its polymerization rate, proving their utility as replacements for TEGDMA as reactive diluents for 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propyloxy) phenyl] propane (Bis-GMA). Copolymer systems containing 2 and 3 showed improved T_g values compared to Bis-GMA/TEGDMA systems.     

Synthesis of hybrid materials via photopolymerization of benzoin functionalized silica nanoparticles

Photopolymerization of methyl methacrylate (MMA) was achieved on the surface of silica nanoparticles by “Grafting from” method. Well defined spherical silica nanoparticles prepared by Stöber method was functionalized with isocyanate groups of toluene di-isocyanate in order to achieve both improved dispersion of nanoparticles in organic solvents and further attachment of benzoin photoinitiator moieties onto the surface of silica nanoparticles. FTIR spectroscopy analysis confirmed the covalent bonding of the functional moieties and grafting of polymethylmethacrylate (PMMA) onto the surface of silica nanoparticles. Thermogravimetric analysis indicated the ratios of attached functionalities and PMMA grafting with a good agreement of SEM observations.     

Synthesis and photopolymerization kinetics of oxime ester photoinitiators

Oxime Ester (OXE) Photoinitiators were synthesized and characterized by HPLC, FTIR, UV–Vis spectra, and ¹H‐NMR. The UV–Vis spectra of these photoinitiators were similar to Benzophenone (BP) but showed large red‐shifted maximum absorption. OXE were not only soluble in many solvents and (meth) acrylate monomers but also could be dispersed easily in propylene glycol monomethyl ether acetate (PGMEA). The kinetics of polymerization of monomer using OXE as photoinitiator was studied by Real‐time infrared (RTIR) spectra. It showed that OXE were an efficient photoinitiator. The concentration of OXE, functionality of monomer, and light intensity had effect on the photopolymerization kinetics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of nylons based on hexadecane diacid

A series of nylons with long alkane segments between amide groups were synthesized by using hexadecane diacid and various diamines, and the resulting polyamides were characterized comprehensively. It was shown that the molecular weights of nylons 6 16, 8 16, 10 16, and 12 16 in our studies exceed 1.1 × 10⁴, whereas nylons 2 16 and 4 16 have relatively low molecular weights. In addition, the melting temperatures, the decomposition temperatures, and the glass transition temperatures of the nylons obtained were measured. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2462–2467, 2003     

新型紫外光产酸剂的合成及其光聚合动力学研究

以2-硝基噻吩,甲基磺酰氯及苯乙腈为原料合成了一种紫外光产酸剂(5-甲磺酸酯亚胺-5H-噻吩-2-亚基)-苯基-乙腈(MTPA),通过傅里叶红外光谱仪、核磁共振仪和紫外吸收光谱仪及热重分析对所合成的产物的结构和性能进行了表征,并利用实时红外(RT-IR)对该引发剂进行了光聚合反应动力学研究。考察了单体、产酸剂浓度对引发速率及单体转化率的影响。结果表明,在一定浓度范围内,随着引发剂浓度增大,聚合速率加快,最终的双键转化率也增高。     

Investigation of PSt-MWCNT concentration on epoxyacrylate photopolymerization and conductivity of polymer films

Photopolymerization kinetics and conductivity changes of epoxyacrylate composites for various loading modified PSt-MWCNT weight fractions changing from 0.0025 to 0.2 wt.% were evaluated by performing photo differential scanning calorimetry (photo-DSC) and four point conductivity measurements. 0.2% PSt-MWCNT additive polymeric films had their electrical conductivity boosted by 6% more than non-additive polymeric films.     

Unique morphology and properties study of polyacrylate obtained via frontal photopolymerization

Remarkable radial temperature distribution at the advancing reaction front was determined in frontal photopolymerization (FPP). Through SEM observation of the cross-fracture section and vertical fracture section for the heat-insulated FPP polymer rod, a cylindrical multi-layer structure was first observed in the FPP product. A sleeve-like model was proposed to describe the unusual morphology on the basis of polymer self-drawing and convection around reaction front. Vertical gradient distribution of molecular weight and its polydispersity in the poly(isobornyl acrylate) rod obtained via FPP was found through GPC determination, which might be developed as an in situ self-fractionation technique for polymer. Thermal analysis of the polymers showed that the FPP tended to produce purer polymer than the traditional thick film photopolymerization.     

H3PW12O40/C催化合成三甘醇双丙烯酸酯的研究

研究了H3PW12O40／C体系对丙烯酸和三甘醇的催化酯化反应,通过对活化温度、共沸剂、催化剂的用量及酸醇摩尔比等因素的优化,酯化率可达91．7％,产品纯度大于98％,并且催化剂可以重复使用多次。     

Photopolymerization kinetics and thermal properties of dimethacrylate based on bisphenol‐S

A dimethacrylate based on bisphenol‐S (DBSMA) was prepared and characterized by Fourier Transform infrared spectroscopy (FTIR), Electrospray Ionisation Tandem Mass Spectrometry (ESI/MS) ¹H NMR, and ¹³C NMR. DBSMA was investigated by a real‐time infrared spectroscopy (RTIR), under different conditions such as varying photoinitiator type and concentration, with and without oxygen, mixing with different amounts of a reactive diluent [1,6‐hexanediol dimethacrylate (HDDMA)]. The mechanical and thermal properties of these curing films were also investigated by dynamic mechanical analysis and thermogravimetric analysis. The results showed homopolymer of DBSMA has better thermal stability than copolymers of DBSMA/HDDMA systems. Also, the cured DBSMA polymer exhibited higher glass transition temperature (T_g) and better thermal stability compared with commercial available resin 2,2‐Bis[4‐(2‐hydroxy‐3‐methacryloxypropoxy)phenyl]propane (BIS‐GMA) (CN151). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A visible light photoinitiator system to produce acrylamide based smart hydrogels: Ru(bpy)3 as photopolymerization initiator and molecular probe of hydrogel microenvironments

A novel visible light bimolecular photoinitiator system (tris(2,2′-bipyridine)ruthenium(II)/N,N-dimethylaniline) is shown to be able to polymerize N-isopropylacrylamide (NIPAM) and 2-Acrylamido-2-Methylpropanesulfonic Acid (AMPS), in aqueous solution, to render high molecular weight polymers and crosslinked gels. The photoinitiator is especially useful to synthesize thermosensitive polymers and gels, because it could be used at temperatures below the phase transition, allowing the polymer chain to grow in its uncoiled state. The polymerization and conversion rates are affected by the structure of the monomer, decreasing in the order NIPAM > AAm > AMPS. The properties of the gels agree with literature data, suggesting that the method is able to produce conventional and smart hydrogels. The microenvironments present near linear polymers and inside crosslinked gels were investigated by measuring fluorescence lifetimes and steady state anisotropy of the metallic complex (Ru(bpy)₃⁺², present in the solution. Clear effects of the polymer presence on the photophysical properties of the complex are observed. Therefore, the same metallic complex could be used as photoinitiator of vinyl polymerization and as molecular probe to sense the hydrogel microenvironments.     

Synthesis of dimethyl-substituted C18 furanoid fatty ester

Reaction of a C₁₈ furanoic fatty acid with dimethyl dicarboxylate (DMAD) furnished the corresponding bicyclo Diels-Alder adduct, which was partially hydrogenated over Pd/BaSO₄. Heat treatment (160–180°C) of the partially hydrogenated product caused a retro-Diels-Alder reaction to yield a furanoid fatty acid derivative containing methoxycarbonyl (COOCH₃) substituents at the 3-and 4-positions of the furan nucleus. Reduction of the COOCH₃ substituents with LiBH₄ gave the corresponding CH₂OH-substituted furanoid fatty acid. Hydrogenation of the latter over Pd/C furnished the desired dimethyl-substituted furanoid acid derivative (overall yield 60%). The spectroscopic properties of the intermediates and product are reported.     

Synthesis and FTIR spectroscopic investigation of the UV curing kinetics of telechelic urethane methacrylate crosslinkers based on the renewable resource—Cardanol

UV curable telechelic urethane–methacrylate crosslinkers based on the natural resource—cardanol was synthesized in a one pot synthetic step involving end capping of isophorone diisocyanate with one equivalent of hydroxyethyl methacrylate followed by condensation with cardanol. The structures of the resins were characterized by ¹H and ¹³C NMR, fourier transform infrared (FTIR) and Matrix‐assisted laser desorption/ionization time of flight (MALDI‐TOF) spectroscopies and size exclusion chromatography (SEC). The curing process and double bond conversion in presence of 2,2‐diethoxy acetophenone as photoinitiator upon UV irradiation was followed by Fourier transform infrared spectroscopy. These hydrogen bonded crosslinkers based on cardanol and its derivatives had higher double bond conversion when compared to a nonhydrogen bonding standard such as hexanediol diacrylate (HDDA) under identical conditions. The temperature effects on the hydrogen bonding were investigated, and a decrease in the extent of double bond conversion with increase in temperature was observed for the telechelic urethane–methacrylate crosslinkers whereas a steady increase in the curing rate was observed for HDDA. This gives direct indication of the influence of hydrogen bonding on the curing process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and cationic photopolymerization of a new fluorinated oxetane monomer

A new fluorinated oxetane monomer (FOX) was prepared using a fluorinated alcohol by phase transfer catalysis in a Williamson ether synthesis. The new fluorinated monomer was used in cationic photopolymerization as comonomer of 3,3′-[oxydi(methylene)]bis(3-ethyloxetane). The presence of the FOX monomer induces a decrease of the glass transition temperature, thermal stabilization and an increase of the final oxetane group conversion. Completely hydrophobic surfaces were obtained with a selective enrichment of the fluorinated comonomer, as confirmed by contact angle and XPS analysis.     

Synthesis and characterization of biodegradable hydrogels based on photopolymerizable acrylate-terminated CL-PEG-CL macromers with supramolecular assemblies of α-cyclodextrins

A series of polypseudorotaxanes were synthesized from α-cyclodextrins (α-CDs) threaded onto photopolymerizable CL-PEG-CL oligomers bearing acrylate terminals. The corresponding supramolecular structured hydrogels were prepared from these polypseudorotaxanes in a mixed solvent of H₂O and DMSO via in situ photopolymerization under UV irradiation. The structure and properties of the gels were characterized by FTIR, TGA-DTG and WAXD. The results show that α-CDs are threaded and immobilized onto the network chains of the hydrogel with crosslinking junctions as stoppers topologically, and the feed molar ratio of α-CDs to the macromers affects the hydrogel structure and the water distribution in the hydrogel. These supramolecular structured hydrogels may be good candidates for biomaterial applications.     

Synthesis and physicochemical characterization of mixed diacid triglycerides that contain elaidic acid

The synthesis of symmetrical and asymmetrical palmito- and stearo-elaidic triglycerides (PEP, SES, EPP, PEE, ESS, and SEE, in which P=palmitic, S=stearic, and E=elaidic acid) was undertaken to investigate their polymorphism. The chemical pathways and the purification steps, including crystallization and adsorption chromatography, are described. The different chromatographic analyses (gas-liquid chromatography: carbon number profile and fatty acid methyl ester profile, and high-performance liquid chromatography) revealed that the purity of the synthesized products was superior to 99% except for SES (>96%). The thermal behavior, as well as the polymorphism of these triglycerides, has been investigated by means of differential scanning calorimetry and powder X-ray diffraction spectroscopy at variable temperatures. The six compounds crystallize according to a double chainlength packing. The most stable polymorphic form of palmito-elaidic triglycerides belongs to the β′ variety, whereas the stearo-elaidic triglycerides are β stable.     

Synthesis of UV-curable tung oil and UV-curable tung oil based alkyd

Two UV-curable tung oil-based resins were synthesized via a Diels–Alder cycloaddition. An UV-curable tung oil (UVTO) was prepared from bodied tung oil and trimethylolpropane trimethacrylate (TMPTMA). An inhibitor, phenothiazine, was added to avoid homopolymerization of TMPTMA. The UV-curable tung oil alkyd (UVTA) was prepared from the monoglyceride process and then reacted with TMPTMA via the Diels–Alder reaction similar to the UVTO. The UVTO and UVTA were characterized by ¹H NMR, ¹³C NMR, and MALDI-TOF mass spectroscopy. The UVTO and UVTA were formulated with a free radical reactive diluent, tripropylene glycol diacrylate (TPGDA) and photoinitiator Irgacure 2100. Photo differential scanning calorimeter (Photo-DSC) was used to investigate curing kinetics of the UVTO and the UVTA. Both the UVTO and UVTA were photocurable with the UVTA formula exhibiting a faster curing speed than the UVTO.