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Polymerization of 2‐hydroxyethyl acrylate in bulk and solution by chemical initiator and by ATRP method
Abstract and Figures
In this study, 2-hydroxyethyl acrylate (HEA) was polymerized to obtain polymers that can be used as hydrogel and copolymerized for biomedical applications. Bulk, solution, and atom transfer radical polymerization (ATRP) techniques at different temperatures were applied. The polymerization in bulk form was carried out in vacuum and in open atmosphere. The polymerization curves showed autoacceleration mechanism and the limiting conversion was 100%. The polymers obtained were insoluable in most common solvents because of high molecular weights and strong intermolecular hydrogen bonding. They absorb more than 30% (w/w) water as hydrogel. To decrease the molecular weight and obtain soluble polymers, HEA was polymerized in solution by ATRP method, which also gave insoluble hydrogel type polymers. The activation energy for bulk polymerization was 155.8 kJ/mol, which is very high for a free radical polymerization. This is due to the high degree of intermolecular hydrogen bonding, which was also supported by FTIR and TGA analysis. The polymers were characterized by FT-IR, DSC, TGA, and 1H NMR techniques. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3957–3965, 2005
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... Additional structural confirmation of LHC was obtained by 1 H NMR (Fig. 4). The chemical shift for vinyl protons (5.5-6.5 ppm) (Vargün and Usanmaz 2005;Kong et al. 2015) disappears in 1 H NMR of LHC, confirming the occurrence of their grafting polymerization onto the lignin backbone ( Fig. 4E and F). A new chemical shift at 4.7 ppm, not observed in a commercial homopolymer Fig. 2 HPLC-UV analyses of HEA depletion by laccase. ...
... Signals at 3.5-4.4 ppm are assigned to protons of -CH 2 in HEA (Fig. 4B) (Vargün and Usanmaz 2005). Aromatic and methoxy proton signal peaks in lignin appeared at 6.0-8.0 ppm and 3.5-4.3 ...
... The protons of -CH and -CH 2 in the backbone of HEA or HEA homopolymer grafted to lignin resonate at 2.25 ppm and 1.51-1.87 ppm (Fig. 4E and F) (Vargün and Usanmaz 2005;Zong et al. 2018). 4.7 ppm nor at 1.5-2.2 ...
Softwood kraft lignin is a major bioresource relevant to the production of sustainable bio-based products. Continued challenges to lignin valorization, however, include poor solubility in organic solvents and in aqueous solutions at neutral pH. Herein, an alkaline tolerant laccase was used to graft acrylate functionalities onto softwood kraft lignin, which is expected to enhance the reactivity of lignin with isocyanate when producing bio-based polyurethanes. Proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and high-performance liquid chromatography were used to confirm successful grafting of the acrylate monomer onto lignin and verify the importance of including tert-butyl hydroperoxide as an initiator in the grafting reaction. Laccase-mediated grafting of softwood kraft lignin under alkaline conditions produced lignin products with approximately 30% higher hydroxyl value and higher reactivity toward isocyanate. The reported enzymatic and aqueous process presents an opportunity for the sustainable valorization of softwood kraft lignin.
Key points
• Softwood kraft lignin displayed high phenolic hydroxyl content, polydispersity index and average molecular weight
• Grafting hydroxyethyl acrylate (HEA) monomer onto kraft lignin by laccase was successful at 60 °C and alkaline conditions
• Lignin-HEA grafted copolymer showed an increase in total OH value and an increase in average molecular weight
... The intensity of the higher wavenumber peaks (2877, 2908, 2938, and 2961 cm -1 ) increases with increasing the electrolyte content due to the formation of hydrogen bonds with free OH [28]. The sharp peak that appears at 1729 cm -1 is assigned to the stretching vibrations of the carbonyl groups (C=O) of 2HPA and vinyl acetate (VAc) monomers [29][30][31]. This peak is slightly blue-shifted by * 2 cm -1 and loses intensity with increasing electrolyte content. ...
... This peak is most probably due to simple hydrolysis of the acetyl groups with the formation of OH [27]. The lower wavenumber peaks at 1435, 1377, and 1234 are related to the CH 2 , CH 3, and C-O vibrations of VAc, while peaks at 1387, 1172, and 1049 cm -1 are corresponding to the CH 3 , O-C=O, and C-O-C vibrations of 2HPA monomers [29,31]. ...
Casting method was employed to prepare films of poly(vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate) (PVVH) terpolymer doped with different amounts of tetrabutylammonium tetrafluoroborate ([TBA][BF4]) electrolyte. The interaction between terpolymer and electrolyte was evident in the shift and reduction of the ATR-FTIR peak intensities of the C–Cl stretching vibrations at 613 cm−1 and 688 cm−1 with increasing electrolyte concentration. The effect of electrolyte was also visible in the reduction of DTG/DTA peak temperature (Tp) of the second stage of the composites. The decrease of the DSC glass transition temperature (Tg) from 344 K to 310 with increasing electrolyte content indicates the plasticization effect of the electrolyte that reduces the inter- and intramolecular interaction maintaining the flexibility of the PVVH terpolymer backbone to bend and slide more readily. The kinetics of thermal degradation of pure compounds and their composites were investigated and discussed in terms of the Coats–Redfern approach. The results revealed an increase in the activation energy of thermal degradation with increasing the electrolyte content. Linear and nonlinear optical parameters were calculated and discussed in terms of the single oscillator model and Miller's rule. The visible and UV transmittance of the investigated materials demonstrated values of 91% and 5%, respectively. Furthermore, they achieved reflectance of 3 and 58% in the visible and UV regions, respectively, making these composites an excellent candidate for optical applications. Besides, the optical conductivity (σop) and dielectric constant of all samples were investigated.
... † An incremental increase in HEA content, ranging from 0 to 30 wt%, is traceable in Fig. 3(a) through the increase in the -OH group peak at 3462 cm −1 . 37 This peak intensity of the -OH group serves as the sole objective indicator for tracking the increase in HEA content. This speci-city is due to overlapping of most other spectral peaks with those of IBOA, as shown in Fig. S4. ...
Herein we introduce a plant oil-based elastomer system for 3D-printable soft robotics, offering high flexibility and resolution. Systems with varied mechanical properties in printed parts enable fast, delicate movements and the shape memory effect.
... Hx protons are associated with only C6+ and capped-C6+ and H b . Even though the reactions were set under a vacuum after completing the reaction, HEA monomers are possibly trapped in the products by hydrogen bonding [43]. The ratio of H a /H b in HEA should be 1. ...
A process for synthesizing UV-curable ester/acrylate precursors from dicarboxylic acid mixtures, oxidized chemical recycling products of HDPE milk bottles, has been developed. The behavior and properties of the non-purified oxidized products were compared to its commercial diacid single components in producing the precursors. Two as-received oxidized products obtained at different conditions, i.e., Oxi-1 and Oxi-2, containing molar compositions of succinic acid (C4): glutaric acid (C5): adipic and longer dicarboxylic acids (C6+) of 55: 23: 22 and 67: 9: 24, were employed. The precursors were produced at high yields by end-capping the carboxylic groups with hydroxyethyl acrylate, utilizing p-TSA catalyst and MEHQ radical scavenger. With 5 mol% p-TSA and 3 wt% MEHQ, a reaction at 120 °C for 2 h was effective for synthesizing the precursors from Oxi-1, Oxi-2, and succinic acid. However, the optimal condition for adipic acid was at 140 °C for 4 h, implying lower esterification reactivity due to its longer methylene sequence. All ester/acrylate precursors were fully cured under UV lights within 10 min. DMA results of cured films from neat precursors (100CL-series) indicate that those derived from longer diacids yielded crosslinked networks with relatively lower Tg and rubbery plateau. However, when only 10% of the precursors were used as crosslinkers for acrylic acid/ethyl-hexyl acrylate (10CL-series), the influence of the starting material’s diacid composition on the film’s properties was lowered. The oxidized products from the nitric oxidation of HDPE have a high potential as value-added starting materials for UV-crosslinkers comparable to those from pure commercial diacids.
... The results obtained by using BP are similar (results not shown). Indeed, neat PHEA exhibits a glass transition temperature at about 13 • C, in agreement with the values reported in the literature [19,46]. Moreover, the addition of the crosslinker slightly increases the polymer T g , a phenomenon which can be ascribed to the reduction of the macromolecular chain mobility. ...
This work aimed to improve the mechanical properties of poly(2-hydroxyethyl acrylate) (PHEA)-based hydrogels by performing their polymerization in the presence of an ad hoc synthesized star-shaped polymer, whose arms are composed of a biopolymer, i.e., polycaprolactone (PCL) end-capped with acrylic units to act as a crosslinker for PHEA. Indeed, this system was designed to have i) biocompatible, biodegradable, and mechanical strong arms as well as ii) a star structure with acrylic functionalities to promote the crosslinking of the material. ¹H-NMR, IR and TGA measurements confirmed the star PCL functionalization, which was carried out starting from a hydroxyl-terminated polymer. Hydrogels were prepared by varying the concentration of the synthesized star polymer, and the properties of the materials obtained by frontal (FP) and bulk polymerization (BP) were compared. Moreover, to evaluate the specific effect of PCL-star-4-2k-tetraacrylate (PCL-TA) on the crosslinking of the systems, samples were also synthesized using a commercial acrylate crosslinker. For what concerns the frontal polymerization process, fronts were found to be stable in the presence of PCL-TA. The thermal characterization results showed a significant decrease in the PHEA glass transition temperature with increasing PCL-TA content, which was particularly evident in the samples prepared by FP. This result can be attributed to the partial miscibility of the two polymers, which become compatible during the polymerization process by forming a copolymer system. This was confirmed by analyzing the thermal behavior of hydrogels polymerized in the presence of a hydroxyl terminated PCL, i.e., a polymer without active functional end groups. The samples synthesized by FP with the star polymer and the commercial crosslinker, as well as neat PHEA, were subjected to mechanical tests. The mechanical behavior of PCL-based hydrogels was outstanding, exhibiting three time higher modulus than that of crosslinked PHEA, and were structurally stable even under high compression loadings. This remarkable property, combined with the fast and efficient polymerization method and the environmentally friendly properties of PCL, make the developed hydrogels promising systems for practical applications in various fields.
... 1-Butanol (BuOH) (99%, extra pure, Acros) was dried over BaO followed by distillation and drying over 4 Å molecular sieves and stored under an argon atmosphere. 2-Hydroxyethyl acrylate (HEA) (97%, Acros) was purified as described elsewhere 37 and stored under an argon atmosphere. 2,2′-Azobis(2methylpropionitrile) (AIBN) (98%, Sigma-Aldrich) was recrystallized from ethanol and dried in a vacuum at 20°C. ...
... Folic acid decomposes in a wide temperature range (100-800 °C) in four overlapping stages; at the temperature of 800 °C, a total weight loss of 73% is observed (Vora et al. 2002). The main decomposition of unmodified polymer (PX-0) and folate-conjugated polymer (PX-(1-4)) occurred in the temperature range between 300 and 450 °C, which is typical of PHEA and PNVCL depolymerization (Vargün and Usanmaz 2005). Non-functionalized polymer (PX-0), and polymers containing the smallest amounts of FA (PX-1 and PX-2) have similar thermal degradation profiles and decompose almost completely in the applied temperature range. ...
Background
In recent years, targeted drug delivery strategies have received special attention from the scientific world due to advantages such as more effective therapy and reduction of side effects. The principle of operation is delayed excretion from the bloodstream of the drug delivery system compared to the drug itself, as well as facilitated penetration into diseased cells thanks to the use of ligands recognized by appropriate receptors. Particularly interesting drug carriers are amphiphilic copolymers that form nano-sized micelles with a drug, which can release the drug at a specific place in the body under the influence of appropriate stimuli.
Results
We describe the synthesis of the diblock polymer, poly(2-hydroxyethyl acrylate)- b -poly( N -vinylcaprolactam) using RAFT/MADIX (Reversible Addition-Fragmentation chain Transfer/MAcromolecular Design by Interchange of Xanthate ) controlled polymerization affording polymers with good dispersity according to SEC ( Size-Exclusion Chromatography ). Some post-modifications of the polymer with folic acid were then performed as evidenced by NMR ( Nuclear Magnetic Resonance ), UV–Vis ( UltraViolet–Visible ) and FT-IR ( Fourier-Transform Infrared) spectroscopy, and TGA ( ThermoGravimetric Analysis ). The formation of stable micellar systems from polymers with and without the drug, 5-fluorouracil, was confirmed by DLS ( Dynamic Light Scattering ) and zeta potential measurements, and TEM ( Transmission Eelectron Microscopy ) imaging. Finally, the cloud point of the polymers was investigated, which turned out to be close to the temperature of the human body. Most importantly, these micellar systems have been explored as a drug delivery system against colon cancer, showing increased cytotoxicity compared to the drug alone. This effect was achieved due to the easier cellular uptake by the interaction of folic acid and its receptors on the surface of cancer cells.
Conclusions
The presented results constitute a solid foundation for the implementation of a nano-sized drug delivery system containing folic acid for practical use in the treatment of drug-resistant cancer, as well as more effective therapy with fewer side effects.
Graphical Abstract
Biological compounds often provide clues to advance material designs. Replicating their molecular structure and functional motifs in artificial materials offers a blueprint for unprecedented functionalities. Here, we report a flexible biomimetic thermal sensing (BTS) polymer that is designed to emulate the ion transport dynamics of a plant cell wall component, pectin. Using a simple yet versatile synthetic procedure, we engineer the physicochemical properties of the polymer by inserting elastic fragments in a block copolymer architecture, making it flexible and stretchable. The thermal response of our flexible polymer outperforms current state-of-the-art temperature sensing materials, including vanadium oxide, by up to two orders of magnitude. Thermal sensors fabricated from these composites exhibit a sensitivity that exceeds 10 mK and operate stably between 15° and 55°C, even under repeated mechanical deformations. We demonstrate the use of our flexible BTS polymer in two-dimensional arrays for spatiotemporal temperature mapping and broadband infrared photodetection.
Monitoring of free and controlled radical homo and copolymerization using automatic continuous online monitoring of polymerization reactions (ACOMP) has been successfully carried out for the past 20 years. An ultraviolet (UV) detector, often combined with a differential refractive index detector (RID), is the usual method to track monomer conversion, but when it comes to copolymerization of monomers with similar UV spectra, it does not suffice for the total decoupling of their signals. Here, Fourier‐transform infrared spectroscopy (FTIR) was coupled to an ACOMP system to separate comonomer conversion while monitoring solution copolymerizations of tert‐butyl acrylate (tBA) and n‐butyl acrylate (nBA). The UV spectra of these comonomers are too similar to allow for separation of their conversions during copolymerizaton. The FTIR region between 1100 and 1410 cm−1, however, shows a strong difference between tBA and nBA peaks – 1403 and 1192 cm−1, respectively. FTIR and UV time dependence for the homopolymerization reactions of each monomer were compared, in order to establish that the FTIR is monitoring the same conversion rates. The reaction rates were determined from the FTIR data and that of tBA was higher than that of nBA. As an initial assessment, the terpolymerization of tBA, nBA, and methyl methacrylate (MMA) was also conducted. Reaction rates were found to be significantly lower, and the 1325 cm−1 peak was successfully used for MMA alone. The incorporation of FTIR into ACOMP opens the path for further expansion to a wide variety of copolymerization reactions, including systems of three or more comonomers. It can be a key new detector in the next steps for development of fully automatic feedback control of composition and molecular weight. This article is protected by copyright. All rights reserved
A novel UV-curable waterborne polyurethane-acrylate (WPUA) was firstly prepared based on hydroxyl telechelic natural rubber (HTNR) via sequential emulsion polymerization. The WPUA was composed of HTNR, Hexamethylene diisocyanate (HDI), 2-hydroxyethyl acrylate (HEA), and the content of hydroxymethyl propionic acid (DMPA) was studied for effects on particle size, stability, and morphology of the new series of WPUA dispersions. The WPUA had a good stability at a total solids content of about 20%. Particle size and dispersion stability slightly decreased with DMPA content. The WPUA gave a good film formation and can provide good wettability with high surface free energy. The mechanical and thermal properties of WPUA film were improved by UV-curing. The effects of photoinitiator (Darocur1173) content were investigated. The UV-cured WPUA films showed better mechanical properties and less water absorption than the not cured WPUA film. Also, the surface wetting was the improvement in the water resistance of the coating on the substrate. In addition, the thermal properties by TGA and the dynamic properties by DMTA slightly increased with photoinitiator dose level due to the higher crosslink density and decreasing the molecular weight between crosslink (Mc) caused the Tg shift to a higher temperature.
The thermal transitions observed in hydrogels based on interpenetrating networks of poly(ethyl acrylate) and poly(hydroxyethyl acrylate) are explained in a simple thermodynamic framework based on the phase diagram that avoids making use of the hypothesis of different “kinds” of water present in the hydrogel. The features that can be explained on its basis include the melting temperature depression of water, the occurrence of crystallization on heating (even when it was absent upon cooling), and the existence of an amount of noncrystallizable water. Three water concentration regimes can be predicted to exist, which give rise to qualitatively different kinds of thermograms.
Crystals of allylurea crystallized from water and methanol have been studied. The unit cell parameters, space groups and densities are for crystals grown from methanol. The tetragonal structure is unstable and changes to monoclinic on standing at room temperature for several months.Allylurea polymerized by Co60 gamma radiation at various temperatures shows a maximum conversion of 60% for crystals grown from water and 40% for crystals grown from methanol. For both cases, “s” type curves were observed. The polymer was shown to be amorphous by X-ray analysis of partially polymerized samples. The polymerization mechanism was shown to be radical from ESR measurements and activation energy (62.4 kJ/mol). Intrinsic viscosities of aqueous solutions of polymer were measured. A maximum value of 0.028 dl/g was observed around 45–50% polymerization conversion at all temperatures.
In this study, the particle size distribution, molecular weight, thermal analysis (TGA) differential scanning calorimetry (DSC) and thermogravimetric analysis, and dynamic mechanical analysis (DMA) of poly(methyl methacrylate) used as dental base material were investigated. The commercial raw material used were prepared for microwave curing, and they were cured by microwave and conventional heat methods. The average particle size of the powder studied (103.1 μm) were much larger than that of the commercial powders (50–78 μm) for conventional curing. The particle size dietribution were almost symmetrical and narrow. The viscosity-average molecular weight were larger for microwave curing and increased with curing time. The glass transition temperature Tg measured (about 110°C) by DSC increased with curing period in microwave oven. The values of Tg were close to each other for both curing techniques. The degradation temperature range observed by TGA were 200–377°C. The movements of molecular chains in their conformations were studied by DMA in the form of changes in different mechanical properties with temperature. It was shown that crosslinking increased with increase of curing time. The changes were more noticeable in microwave curing compared to conventional heat curing. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2971–2978, 1999
Radiation-induced polymerization of 1,2-epoxy-4-epoxyethylcyclohexane (EECH) has been carried out at different temperatures in solid and liquid states. Activation energy was calculated from Arrhenius plot and ionic mechanism was proposed. Molecular weights for some polymer samples were determined by cryscopic method and compared with their intrinsic viscosities. Cationic polymerization of EECH initiated by BF3 · O(C2H5)2 and anionic polymerization initiated by NaOH are also studied. Two epoxy rings can be opened for polymerization selectively by radiation, but not by chemical initiators. The expected polyether structure was observed from the IR spectrum. Polymers obtained were shown to be amorphous from X-ray photographs.
The controlled/“living” radical polymerization of n-butyl acrylate (n-BA) and 2-trimethylsilyloxyethyl acrylate (TMS−HEA) by atom transfer radical polymerization (ATRP) is reported. Di- and triblock copolymers with predefined block lengths and low polydispersities were obtained, using methyl 2-bromopropionate as the initiator, CuIBr as catalyst and N,N,N‘,N‘‘,N‘‘-pentamethyldiethylenetriamine as the ligand. Hydrolysis of the trimethylsilyl groups led to block copolymers with n-BA and 2-hydroxyethyl acrylate (HEA) units which were characterized by SEC, 1H NMR, and DSC. Diblock copolymers of n-BA and HEA could also be obtained by successive addition of the two monomers, in that order. The amphiphilic di- and triblock copolymers formed dispersions in water.
The solid-state polymerization of N-vinylcarbazole initiated by UV-radiation at 25, 32.5, and 45°C was studied. The rate of polymerization increased with increase in temperature. The limiting conversion at all temperatures is 56%. The molecular weight, determined by viscosity measurements, first increased, reached a maximum, then decreased. The molecular weight distribution, studied by GPC, was broad with a shoulder on the low molecular weight side. The morphology of partially polymerized single crystals was studied by electron scanning microscopy to determine the propagation mode of polymerization with respect to the monomer structure. The high activation energy of 71-9kJ/mol and ESR spectrum suggest a radical mechanism of polymerization.
Poly(ester urethane) (PU) with functional groups (amide, hydroxyl, carboxyl) on surfaces were prepared by grafting monomers such as acrylamide (AAm), hydroxyethyl acrylate (HEA), and methacrylic acid (MAA) onto the PU membranes. Grafting copolymerization was carried out by the combined use of photooxidization and UV irradiation grafting. The PU membrane was photooxidized in hydrogen peroxide solution under UV light to yield hydroperoxide groups on the surface and then irradiation grafting with monomer in water. The ATR-FTIR spectrum, X-ray photoelectron spectroscopy characterized the grafted copolymers and verified the occurrence of grafting copolymerization. The results showed that the content of hydroperoxide groups yielded was dependent on the photooxidization time and reached maximum at about 8 h. Grafting copolymerization was enhanced when irradiating by UV light. The degree of grafting was increased with the increase of content of hydroperoxide groups, irradiation time, and monomer concentration. The grafting copolymerization was enhanced when an appropriate amount of ferrous ions was added. After grafting, the wettability of PU and the water absorption percentage increased with the degree of grafting. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2505–2512, 2000
The thermal and mechanical properties of dental base materials cured by microwave and conventional heat methods were studied. The commercial dental base poly(methyl metacrylate) (PMMA) powder and liquid were mixed in a 3/1 ratio. They were polymerized by a peroxy catalyst at 65°C, then cured with a boiling water temperature and microwave radiation for periods of 5, 10, 15, 20, 25, 30, and 35 min for heat curing and 1, 2, 3, 5, and 7 min for microwave radiation. The microwave radiation outputs used were 500 and 700 W. The products of 5-min heat curing and 1-, 2-, and 7-min microwave curing were soluble in chloroform. All the others were partially soluble. The viscosity-average molecular weights of the soluble samples were about 1 × 106. The thermal properties of the polymer samples were studied by differential scanning calorimetry (DSC). For the samples that were not cured completely, broad exothermic peaks at around 125°C were obtained in the DSC thermograms. The glass-transition temperatures for completely cured samples were 110–120°C. The mechanical properties of the samples were determined from tensile and three-point bending tests. The elastic modulus was highest for samples obtained by the conventional method with a 30-min curing period. However, the bending modulus was highest for 7-min cured samples in a 700-W microwave. The mechanical strengths of the 700-W output were higher than those at 500 W. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 251–256, 2003
The application of atom transfer radical polymerization (ATRP) to the homopolymerization of 2-hydroxyethyl acrylate, a functional monomer, is reported. The polymerizations exhibit first-order kinetics, and molecular weights increase linearly with conversion. Polydispersities remain low throughout the polymerization (Mw/Mn ≈ 1.2). Reactions were conducted in bulk and in 1 : 1 (by volume) aqueous solution; the latter demonstrates the resilience of ATRP to protic media. Analysis of poly(2-hydroxyethyl acrylate) by MALDI-MS and 1H-NMR shows Mn,exp to be much closer to Mn,th than those observed by SEC using polystyrene standards. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1417–1424, 1998