Showing papers on "Bulk polymerization published in 2022"
TL;DR: In this article , the influence of the redox-initiating composition on the course of polymerization and the mechanical properties of bone cement was analyzed, and the best reaction conditions were provided by an initiating system containing 0.3 wt.% of BPO oxidant and 0.5 wt% of DMA reductant.
Abstract: Background: The amount of oxidant (initiator) and reductant (co-initiator) and their ratio have a significant effect on the properties of polymethacrylate bone cement, such as maximum temperature (Tmax), setting time (tset) and compressive strength (σ). The increase in the initiating system concentration causes an increase in the number of generated radicals and a faster polymerization rate, which shortens the setting time. The influence of the redox-initiating composition on the course of polymerization (rate of polymerization and degree of double bond conversion) and the mechanical properties of bone cement will be analyzed. Methods: Bone cements were synthesized by mixing a powder phase composed of two commercially available methacrylate copolymers (Evonic) and a liquid phase containing 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and triethylene glycol dimethacrylate (D3). As an initiating system, the benzoyl peroxide (BPO) as an oxidant (initiator) in combination with a reducing agent (co-initiator), N,N-dimethylaniline (DMA), was used. Samples were prepared with various amounts of peroxide BPO (0.05%, 0.1%, 0.2%, 0.3%, 0.5% and 0.7% by weight) with a constant amount of reducing agent DMA (0.5 wt.%), and various amounts of DMA (0.25%, 0.35% and 0.5% by weight) with a constant amount of BPO (0.3 wt.%). The polymerization kinetics were studied by differential scanning calorimetry (DSC). Doughing time and compressive strength tests were carried out according to the requirements of the ISO 5833:2002 standard. Results: The increase in polymerization rate was due to the increase in the amount of BPO. In addition, the curing time was shortened, as well as the time needed to achieve the maximum polymerization rate. The final conversion of the double bonds in the studied compositions was in the range 74–100%, and the highest value of this parameter was obtained by the system with 0.3 wt.% of BPO. The doughing times for each BPO concentration were in the range of 90–140 s. The best mechanical properties were obtained for the cement following the initiating system concentrations: 0.3 wt.% of BPO and 0.5 wt.% of DMA. Nevertheless, all tested cements met the requirements of the ISO 5833:2002 standard. Conclusions: Based on the conducted polymerization kinetic studies, the best reaction conditions are provided by an initiating system containing 0.3 wt.% of BPO oxidant (initiator) and 0.5 wt.% of DMA reductant (co-initiator). A decrease in the DMA amount caused a decrease in the polymerization rate and the amount of heat released during the reaction. The change in BPO and DMA concentrations in the composition had little effect on the doughing time of the studied bone cement. The cements showed similar doughing times, ranging from 90–225 s, which is comparable to the bone cement available on the market.
12 citations
TL;DR: In this article , the role of functional groups on the polymerization rate in the presence or absence of graphene oxide was investigated, and the results showed that the presence of GO results in a dissociation of hydrogen bonds between monomer and polymer molecules, leading to higher reaction rates.
Abstract: Functional groups in a monomer molecule usually play an important role during polymerization by enhancing or decreasing the reaction rate due to the possible formation of side bonds. The situation becomes more complicated when polymerization takes place in the presence of graphene oxide since it also includes functional groups in its surface. Aiming to explore the role of functional groups on polymerization rate, the in situ bulk radical polymerization of hydroxyethyl acrylate (HEA) in the presence or not of graphene oxide was investigated. Differential scanning calorimetry was used to continuously record the reaction rate under both isothermal and non-isothermal conditions. Simple kinetic models and isoconversional analysis were used to estimate the variation of the overall activation energy with the monomer conversion. It was found that during isothermal experiments, the formation of both inter- and intra-chain hydrogen bonds between the monomer and polymer molecules results in slower polymerization of neat HEA with higher overall activation energy compared to that estimated in the presence of GO. The presence of GO results in a dissociation of hydrogen bonds between monomer and polymer molecules and, thus, to higher reaction rates. Isoconversional methods employed during non-isothermal experiments revealed that the presence of GO results in higher overall activation energy due to the reaction of more functional groups on the surface of GO with the hydroxyl and carbonyl groups of the monomer and polymer molecules, together with the reaction of primary initiator radicals with the surface hydroxyl groups in GO.
5 citations
5 citations
TL;DR: Trimethylene carbonate, the monomer that can be prepared from CO2 and 1,3-propanediol, was polymerized cationically according to the activated monomer mechanism, as follows from the polymerization kinetics and the DFT studies as discussed by the authors .
2 citations
TL;DR: In this article, BPO and DMT were chosen to initiate the radical polymerization of MMA (methyl methacrylate) in order to optimize the initiator concentration through reaction rate of polymerization progress and properties of PMMA.
Abstract: Vinyl polymerization is an important path for in-situ polymerization of thermoplastic resins. BPO (Benzoyl peroxide) and DMT (dimethyl-p-toluidine) were chosen to initiate the radical polymerization of MMA (methyl methacrylate) in this work. Optimization of initiator concentration was studied through reaction rate of polymerization progress and properties of PMMA (polymethyl methacrylate). At first, the catalytic of DMT in MMA polymerization was studied through polymerization experiments and rheological experiments. Results showed that DMT could catalyze more than one molecular BPO in the whole reaction period. It can catalyze the decomposition of BPO after being connected to PMMA chains. Second, the BPO: DMT ratio was set to 2:1 to study the ideal content by comparing the mechanical properties of PMMA. Results showed that with the increase of initiator contents, T g , molecular weight, and residual monomer were all declining. Meanwhile, the mechanical properties of PMMA matrix first increased and then decreased. This phenomenon was analyzed by 1H-NMR and SEM. And the optimal BPO-DMT concentration was 1.0 mol%–0.5 mol%. Graphical Abstract
20 Jan 2022
TL;DR: Acrylonitrile homopolymerization initiated by p-nitrophenacyldimethyl sulfonium ylide exhibits non-ideal kinetics, with monomer and initiator exponents of 1.1 and 0.39, respectively, and an overall activation energy of 44 kJ/mol under inert atmosphere.
Abstract: Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208 016, India E-mail : sskatiyar@yahoo.com Fax : 91-512-570006 Manuscript received 3 November 2000 Homopolymerization of acrylonitrile, initiated by p-nitrophenacyldimethyl sulfonium ylide has been studied at 40o under inert atmosphere using dilatometric technique. The radical polymerization of acrylonitrile follows non-ideal kinetics, since the monomer and initiator exponent values are found to be 1.1 and 0.39, respectively. The polymerization is retrarded by hydroquinone. The overall activation energy is calculated to be 44 kJ mol-1• Kinetic data indicate that the polymerization involves free radical mechanism.
TL;DR: In this paper , a reverse atom transfer radical polymerization (RATRP) was used to synthesize poly(dimethyl itaconate) (PDMI) using an AIBME/CuBr2/dNbpy system.
Abstract: Reverse atom transfer radical polymerization (RATRP) was used to synthesize poly(dimethyl itaconate) (PDMI) using an AIBME/CuBr2/dNbpy system. The number average molecular weight (Mn) of PDMI was as high as Mn = 15 000 g mol−1, the monomer conversion rate reached up to 70%, and the dispersity remained low (Đ = 1.06–1.38). The first-order kinetics of PDMI are discussed in detail. The AIBME initiator had a higher initiation efficiency than the AIBN initiator. As the ratio of initiator (AIBME) to catalyst (CuBr2) decreased, the Mn and Đ of PDMI decreased. At 60 °C and 80 °C, the Mn of PDMI was much higher than the theoretical number average (Mn,th), and the Đ of PDMI broadened with the conversion rate. At 100 °C, the Đ of PDMI remained low, and the Mn of PDMI was closer to the Mn,th. As the ratio of monomer (DMI) to initiator (AIBME) increased, the Mn of PDMI changed little over time. These phenomena could be explained by the influence of the initiator and catalyst on polymerization kinetics.
TL;DR: In this paper , a photodriven radical-mediated [3 + 2] cyclopolymerization (PRMC) was proposed based on the results of theoretical calculations and experimental measurements.
1 Apr 2022
Abstract: Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta-700032. Manuscript received 14 July 1976 ; revised 14 September 1976 ; accepted 12 January 1977 Polymerization of methyl methacrylate by N-bromosuccinimide/vanadyl sulfate as redox initiator in aqueous solutions has been studied. N-bromosuccinimide by itself cannot initiate polymerization in dark but, does so strongly in presence of reducing metal salts e.g., Fe2+, VO2+, Cu2+, Ti3+ etc (in aqueous medium) even in dark. However, in presence of U.V. light N-bromosuccinimide can be used as a good initintor. The rate of polymerization under nitrogen atmosphere at 40 \(\pm\)0.1˚C is proportional to the square-root of N -bromosuccinimide concentration (1.0 x 10-4 - 9.0 x 10-4 mol. l.-1) and proportional to the first power of monomer concentration (1.88 x 10-2 -9.40 x 10-2 mol. l.-1) within the range studied. However, the effect of activator concentration, VOSO4, on the polymerization rate shows an interesting trend. The polymerization rate shows an usual square-root dependence on the activator concentration within the range 1.0 x 10-4 - 5.0 x 10-4 mol.l.-1 But as the activator concentration is increased beyond 5 x 10-4 mol. l.-1, the polymerization rate becomes almost independent of the activator concentration. The overall activation energy is about 5.25 K. cal/mole. Inorganic electrolytes depress the rate of polymerization whereas an emulsifier enhances it, pH of the medium (neutral or acidic) does not have much influence on the polymerization rate down to the value of 4.00. However, at pH 3.00, the rate is decreased considerably. The polymer samples are characterized by the absence of hydroxyl, halogen and sulfate end groups. Polymerization through succinimidyl radical was suggested to account for the unusual end group profile. Based on our findings suitable mechanism of initiation and termination has been proposed.