Radical Bulk Polymerization Research Articles

Preparation and thermal properties of a novel flame retardant copolymer

A monomer, acryloxyethyl phenoxy phosphorodiethyl amidate (AEPPA), was synthesized and characterized using Fourier transform infrared (FTIR), 1H nuclear magnetic resonance spectroscopy ( 1H NMR) and 31P NMR. The copolymer with various amounts of styrene (St) was obtained by the free radical bulk polymerization between AEPPA and St, and characterized using 1H NMR. The thermal properties of the copolymers were investigated with thermogravimetric analysis (TGA) in air and nitrogen atmosphere, and differential scanning calorimetry (DSC). The TGA results in air indicated the copolymers with AEPPA show higher thermal stability than those without AEPPA. However, the TGA results in nitrogen showed that the decomposition temperature decreased and the char residue increased with the increase of AEPPA. The glass transition temperature ( T g) of the copolymers from DSC indicated that a inverse proportion was observed between T g and the amount of AEPPA incorporated. The flammability of the copolymers was evaluated by microscale combustion calorimeter (MCC). The MCC results showed that AEPPA can decrease the peak heat release rate (PHRR) and the heat release capacity (HRC), and the sample CP10 shows the lowest PHRR and HRC.

Synthesis and characterization of quaternary ammonium PEGDA dendritic copolymer networks for water disinfection

AbstractQuaternary ammonium compounds are some of the most widely used antimicrobial agents for various medical applications due to their low toxicity and broad spectrum antimicrobial activity. Various generations of poly(ethyleneglycol)diacrylate (PEGDA) based dendrimers were synthesized by Michael addition reaction of PEGDA with ethylene diamine and diethyl amine. The percentage yield of different generation of dendrimers were 70%, 66%, 60%, and 85% for G1.0 (=), G1.5 (NH2), G2.0 (=), and G2.5 (=, NEt2), respectively. Synthesized dendrimers were also copolymerized with ethyleneglycol dimethacrylate by free radical bulk polymerization at room temperature using ammonium persulphate/N,N,N′,N′‐tetramethyl ethylenediamine as a redox initiator system to form dendritic copolymer networks. These networks were quaternized with hydrochloric acid by continuously refluxing at 40°C for 6 h. Dendrimers and quaternized dendritic copolymer networks were characterized by 1HNMR, FTIR, Differential scanning calorimetry, Thermogravimetric analysis, Scanning electron microscope, swelling, and leaching studies. Synthesized quaternary ammonium dendritic copolymer networks were found to be biostable and insoluble in water and capable of killing both Gram‐positive and Gram‐negative bacteria when contaminated water was treated with them. It was also observed that antimicrobial efficiency of dendritic copolymer networks increases with the increase in nitrogen atoms in the copolymer. The dendritic copolymer network with 16 quaternary ammonium groups (G2.5 (=, NEt2): EGDMA QHCl) were highly efficient to disinfect 10 mL bacterial solution of 2000 cfu/mL within 2 min even at a very low concentration of 0.005 g/mL. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The effect of addition of acrylic acid and thioglycolic acid on the nanostructure and thermal stability of PMMA–montmorillonite nanocomposites

Poly(methyl methacrylate) (PMMA)/organophilic montmorillonite (OMMT) nanocomposites were synthesized by the in situ free radical bulk polymerization of methyl methacrylate. The effect of small amount of acrylic acid as the co-monomer and thioglycolic acid as the chain transfer agent on the nanostructure of these nanocomposites was investigated by X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) analyses. No reflection was discernible in the XRD patterns of all samples. In SAXS experiments, a great amount of small clay montmorillonite aggregates (less than 40 Å) were observed. The acrylic acid used as the co-monomer increased the affinity between the montmorillonite and the polymer, resulting in better dispersion of the montmorillonite particles. The glass transition temperature of the nanocomposites was evaluated by differential scanning calorimetry (DSC) and the thermal stability was investigated by thermogravimetric studies (TGA). As expected, the presence of the montmorillonite increased the glass transition temperature. The thermal stability of nanocomposites was distinctly higher than of pure PMMA and was increased by the presence of small amounts of acrylic acid as the co-monomer.

Effect of temperature on initial stage of methyl methacrylate free radical bulk polymerization

Classic theory of free radical polymerization is based on two assumptions. The first is that the concentration of initiator is slightly changed and could be taken as a constant value. The second assumption is that the rate of initiation is equal to the rate of termination. Equation for the polymerization rate based on these assumptions can not successfully describe the initial stage of free radical polymerization. In order to solve this problem, three mathematical models were developed and used to verify of the mentioned assumptions. The models were fitted to experimental data and qualities of their fits were compared. Experimental data of isothermal bulk polymerization of methyl methacrylate were obtained by differential scanning calorimetry at 60, 70, 80 and 90?C with initiator concentration (AIBN) of 0.5 wt%. The best fit was shown by the model that assumes constant concentration of initiator during initial stage but takes into account that the rate of initiation is not equal to the rate of termination at the beginning.

Ferroferric oxide/polystyrene (Fe3O4/PS) superparamagnetic nanocomposite via facile in situ bulk radical polymerization

Organo-modified ferroferric oxide superparamagnetic nanoparticles, synthesized by the coprecipitation of super- paramagnetic nanoparticles in presence of oleic acid (OA), were incorporated in polystyrene (PS) by the facile in situ bulk radical polymerization by using 2,2-azobisisobutyronitrile (AIBN) as initiator. The transmission electron microscopy (TEM) analysis of the resultant uniform ferroferric oxide/polystyrene superparamagnetic nanocomposite (Fe3O4/PS) showed that the superparamagnetic nanoparticles had been dispersed homogeneously in the polymer matrix due to the sur- face grafted polystyrene, confirmed by Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). The superparamagnetic property of the Fe3O4/PS nanocomposite was testified by the vibrating sample magnetome- ter (VSM) analysis. The strategy developed is expected to be applied for the large-scale industrial manufacturing of the superparamagnetic polymer nanocomposite.

Evaluation of the Final Morphology of HIPS Based on the Architecture of the Compatibilizer Graft Copolymer PBd‐g‐PS

AbstractHigh Impact Polystyrene (HIPS) was synthesized by radical bulk polymerization at 70 °C using 6% w/w of total rubber and 0.01% w/w of azobisisobutyronitrile (AIBN) as radical initiator, where the total rubber was composed by polybutadiene (PBd) and model graft copolymers PBd‐g‐PS. Different ratios in weight percent of PBd to PBd‐g‐PS were used in order to evaluate the effect of the graft copolymers on the morphology development of the rubber particles during the HIPS synthesis reaction. The morphology of the final material was evaluated by Transmission Electron Microscopy (TEM). The model graft copolymers used with controlled architecture and molecular weight were synthesized previously by high vacuum anionic polymerization. Results show that increasing the content and changing the architecture of the graft copolymer significantly affects the phase inversion point.

Synthesis and characterization of novel glucose- and lactose-containing methacrylate-based radiopaque glycopolymers

Two kinds of glucose- and lactose-containing methacrylate-based radiopaque glycopolymers (MGI and MLI) were synthesized and characterized. The first glycopolymer was prepared from 2-(2′,3′,4′,6′-tetra- O-acetyl-β- d-glucosyloxy)ethyl methacrylate (AcGEMA), 2-(2′-iodobenzoyl)-ethyl methacrylate (2-IEMA) and methyl methacrylate (MMA) via bulk radical polymerization, followed by the deacetylation. The second glycopolymer was synthesized directly from 2-lactobionamidoethyl methacrylate (LAMA), 2-IEMA and MMA via radical polymerization in DMSO. The cleavage of the ester bond in 2-IEMA of MGI was determined by 1H NMR analysis during the deacetylation. The in vitro radiopacity of these glycopolymers was demonstrated with both an X-ray detector and a CT scanner. The in vivo CT-imaging tests performed by intravenous administration of a saline solution containing the selected MLI sample in a mouse model exhibited enhanced visibility of the liver and kidney organs.

Preparation and photocatalytic activity of zinc sulfide/polymer nanocomposites

AbstractZnS nanoparticles were prepared on the surface of polyacrylonitrile (PAN) and methyl methacrylate (MMA)/butyl methacrylate (BMA)/acrylic acid (AA) copolymer nanofibers. The MMA–BMA–AA copolymer was synthesized by bulk radical polymerization using 2,2′‐azobisisobutyronitrile as the initiator. The PAN and MMA–BMA–AA copolymer nanofibers were prepared by electrospinning. Zinc ions were introduced onto the surface of the nanofibers by coordination with the carboxyl of AA. Then, sulfide ions were added to react with zinc ions to form ZnS nanoparticles. The average diameter of the nanofibers was about 300 nm, and the diameter of the ZnS nanoparticles was about 10 nm. The band position of the photoluminescence spectrum of the ZnS/PAN and MMA–BMA–AA nanocomposites had an 80‐nm blueshift in comparison with that of the corresponding bulk ZnS sample. The ZnS/PAN and MMA–BMA–AA nanocomposites had high photocatalytic activity for the degradation of phenol under ultraviolet irradiation; the photocatalytic activity changed indistinctively after it was used repeatedly (6 times). The nanofibers of PAN and MMA–BMA–AA not only dispersed but also stabilized the ZnS nanoparticles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Thermal properties of PS/TiO 2 nanocomposites obtained by in situ bulk radical polymerization of styrene

TiO 2 nanoparticles, surface modified with 6-palmitate ascorbic acid, were incorporated in polystyrene (PS) by in situ bulk radical polymerization of styrene using 2,2′-azobisisobutyronitrile as initiator. The molar mass and polydispersity of synthesized samples were estimated by gel permeation chromatography. The influence of surface modified TiO 2 nanoparticles on the thermal properties of PS matrix was examined using thermogravimetry and differential scanning calorimetry. Molar mass and polydispersity of PS were not influenced by the presence of the TiO 2 nanoparticles. On the other hand, PS/TiO 2 nanocomposites have higher glass transition temperature and better thermal and thermooxidative stability than the pure PS.

Controlled degradation of poly(ethyl cyanoacrylate-co-methyl methacrylate) (PECA-co-PMMA) copolymers

Copolymers of poly(ethyl cyanoacrylate-co-methyl methacrylate) (PECA-co-PMMA) with various compositions were synthesized by free radical bulk polymerization in an effort to control degradation and stability as well as glass transition temperature to overcome intrinsic poor processability of the poly(ethyl cyanoacrylate) (PECA) homopolymer. The copolymers were found to have an alternating random tendency, which was responsible for the efficient inhibition of the unzipping degradation from the polymer chain. Consequently, the stability of the copolymers at elevated temperature and in solution was significantly improved compared to the PECA homopolymer. The glass transition temperatures of the copolymers were lowered by the incorporation of the methyl methacrylate (MMA), thereby further widening the operating temperature range of the polymer. On the other hand, the copolymer films exhibited hydrolytic degradation in phosphate buffered saline (PBS) solution at 37°C, which is promising for their use as novel biomaterials.

Influence of cubic α-Fe 2O 3 particles on the thermal stability of poly(methyl methacrylate) synthesized by in situ bulk polymerization

Poly(methyl methacrylate)/α-Fe 2O 3 composites were prepared by in situ bulk radical polymerization of methyl methacrylate in the presence of the cubic α-Fe 2O 3 particles using 2,2′-azobisisobutyronitrile as initiator. The cubic α-Fe 2O 3 particles were synthesized by forced hydrolysis of FeCl 3 and characterized by X-ray diffraction analysis and transmission electron microscopy. The molar masses and molar mass distribution of synthesized PMMA samples were determined by gel permeation chromatography. The influence of α-Fe 2O 3 filler particles on the thermal properties of the PMMA matrix was investigated using thermogravimetry and differential scanning calorimetry. The molar mass and polydispersity of PMMA extracted from composite samples were not influenced by cubic α-Fe 2O 3 particles. The obtained composites have better thermal and thermooxidative stability than pure PMMA. On the other hand, the values of the glass transition temperature of composite samples were identical to the glass transition temperature of pure PMMA.

Fast responsive poly(acrylic acid‐co‐N‐isopropyl acrylamide) hydrogels based on new crosslinker

AbstractNovel dual temperature‐ and pH‐sensitive poly(acrylic acid‐co‐N‐isopropylacrylamide), AA/NIPAAm, hydrogels were successfully prepared by chemical crosslinking with crosslinkers. Copolymers of AA/NIPAAm were crosslinked in the presence of different mol % of N,N‐methylene bisacrylamide (MBA) and melamine triacrylamide (MAAm) as crosslinkers by bulk radical polymerization. The resultant xerogels were characterized by extracting the soluble fractions and measuring the equilibrium water content. Lower critical solution transition temperatures (LCST) were measured by DSC. The properties of crosslinked AA/NIPAAm series are evaluated in terms of compositional drift of polymerization, heterogeneous crosslinking, and chemical structure of the relevant components. Soluble fractions of the crosslinked networks were reduced by varying the MAAm and MBA concentrations. The influence of environmental conditions such as temperature and pH on the swelling behavior of these polymeric gels was investigated. The swelling behaviors of the resulting gels show pH sensitivity. The prepared MAAm type AA/NIPAAm hydrogels exhibited a more rapid deswelling rate than MBA type AA/NIPAAm hydrogels in ultra pure water in response to abrupt changes from 20°C to 50°C. The results of this study provide valuable information regarding the development of dual stimuli‐sensitive hydrogels with fast responsiveness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Comparison of conventional and controlled bulk polymerization of styrene by N-methyl-2-pyrrolidone and 1-dodecanethiol

AbstractControlled radical polymerization of styrene was initiated using Nmethyl- 2-pyrrolidone (NM2P) and 1-dodecanethiol (1DT). This polymerization system exhibited “living” characteristics, namely the molecular weight averages of resulting polymers increased linearly with conversion, which has been determined by gel permeation chromatography (GPC) analysis. The polymer was additionally characterized with Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. Kinetics of controlled radical polymerization has been studied and the temperature dependency of overall polymerization rate constant has been determined. A comparison of conventional bulk radical and controlled bulk radical polymerization of styrene has been explored. Conventional radical polymerization was initiated with 2,2’-azobis(2- methylpropionitrile) (AIBN), whereas 1-dodecanethiol was applied as a chain transfer agent. The reaction rate of controlled radical polymerization was slower than the reaction rate of conventional radical polymerization initiated with AIBN. Consequentially, the activation energy and the pre-exponential factor were lower in the case of controlled polymerization in comparison to the ones observed in the conventional - AIBN initiated - system. Furthermore, by comparing the controlled to the conventional radical polymerization lower polydispersities were observed. Macromolecular structure analysis suggested a more linear chain structure in the controlled radical polymerization system. The thermal properties of polymer products have also been studied and the corresponding glass transition temperatures were higher upon comparison of the conventional and the AIBN initiated system, respectively

Facile graft polystyrene onto multi-walled carbon nanotubes via in situ thermo-induced radical polymerization

A facile procedure was developed for the grafting of polystyrene onto the surfaces of multi-walled carbon nanotubes (MWNTs) via the in situ thermo-induced bulk radical polymerization of styrene at the different polymerizing temperatures, in the presence of MWNTs without any initiator added. The grafting products were validated by the dispersibility, TEM, TGA, FT-IR, and Raman analysis. The TGA results also showed the lower polymerizing temperature was propitious to the free radical addition reactions.

Stereochemical elucidation of complex α‐methyl and β‐methylene carbon resonances in poly(2‐hydroxy ethyl methacrylate‐co‐methacrylonitrile) by 2D NMR

AbstractCopolymers of 2‐hydroxy ethyl methacrylate and methacrylonitrile (H/M) of different composition were synthesized by free radical bulk polymerization using azobisisobutyronitrile (AIBN) as an initiator under nitrogen atmosphere. The copolymers composition were calculated from 1H and quantitative 13C{1H}NMR spectra. The complete spectral assignment of complex and overlapped α‐methyl and β‐methylene carbon regions in 13C{1H} NMR spectrum in term of compositional and configurational sequences of H/M copolymers were done with the help of two‐dimensional heteronuclear single quantum coherence (HSQC) and total correlation spectroscopy (TOCSY). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Radical polymerization of methyl methacrylate in the presence of low-molecular-weight poly(methyl methacrylate)

The kinetics of the bulk radical polymerization of methyl methacrylate and the structure and properties (physicomechanical and thermomechanical, as well as diffusion and sorption) of the polymers were examined in relation to the amount of low-molecular-weight poly(methyl methacrylate) added.

Noncovalent Cross-Linking of Poly(methyl methacrylate) via Polypseudorotaxane

Free radical bulk polymerization of methyl methacrylate (MMA) was carried out in the presence of a macrocyclic amine based on cyclic polystyrene. The polymer changed to an insoluble solid upon heating at 180 °C in a vacuum. The insolubility is attributed to the in situ formation of a polypseudorotaxane, followed by the covalent fixation of the threaded ring segment with the linear chain to form a noncovalent three-dimensional structure.

Thermal Stabilities of Attapulgite/Polystyrene (ATP/PS) Nanocomposites via Microwave‐Assisted Bulk Polymerization

Attapulgite/polystyrene (ATP/PS) nanocomposites with different contents of attapulgite nano‐needles organo‐modified, and cetyltrimethylammonium bromide (CTAB) were successfully prepared by the in situ bulk radical polymerization of styrene, under microwave irradiation. The transmission electron microscopy (TEM) results showed good dispersibility of the organo‐modified attapulgite nano‐needles in the polystyrene matrices. The thermogravimetric analysis (TGA) revealed that the thermal stability of the nanocomposite was enhanced with the increase of additional attapulgite nano‐needles.

Stereoregularity evolution of methyl acrylate and vinyl acetate copolymers by 2D NMR spectroscopy

Copolymers of methyl acrylate (M) and vinyl acetate (V) were synthesized by free radical bulk polymerization using azobisisobutyronitrile (AIBN) as an initiator at 70 °C and their composition were calculated from 1H NMR spectra. These copolymer compositions were further used to calculate reactivity ratios of V/M copolymers. The reactivity ratios obtained from linear Kelen–Tudos (KT) and non-linear error-in-variable methods (EVM) are r M = 6.74 ± 1.03, r V = 0.04 ± 0.01 and r M = 6.72, r V = 0.04, respectively. The copolymers were analyzed for their stereochemical structure utilizing various 1D ( 1H, 13C{ 1H}, DEPT) and 2D (HSQC, TOCSY, HMBC) NMR techniques. 2D HSQC and TOCSY NMR experiments were employed to resolve the highly overlapped and complex 1H and 13C{ 1H} NMR spectra of copolymers. The complete spectral assignment of carbonyl carbons were done with the help of 2D HMBC spectra. The carbonyl carbon was found to be sensitive up to pentad configurational sequences and shows three and four bond couplings with methine and methylene protons.

Reactivity ratios determination and NMR characterization of 2-hydroxy ethyl methacrylate and methyl methacrylate copolymers

Reaction of 2, 2'-dipyridylamine (DPA) with hexafluorophosphoric acid (HPF6) in methanol generates white rod-shaped crystals of HDPA.PF6,H 2O. The salt is characterised by C, H and N analyses, FT-IR, 1H NMR, mass spectroscopy and molar conductance measurement. The X- ray crystal structure of the salt has been determined. The structure shows that the salt is monomeric. The amine nitrogen is strongly hydrogen bonded with oxygen atom of water. Two pyridyl rings are almost planar which is a rarity in the coordination chemistry of DPA. Semi- empirical AM1 calculation was also Abstract : NMR has proven to be one of the most informative technique for the investigation of copolymer microstructure as chemical shifts are sensitive to compositional and configurational sequences of copolymers. The HEMA/MMA copolymers were prepared by free radical bulk polymerization at 70 oC. The copolymer composition was determined from 1H NMR spec trum which is then used to determine the reactivity ratios. The reactivity ratios obtained from KT, EVM and least square methods are r HEMA = 0.98, r MMA = 0.82; r HEMA = 0.88, r MMA = 0.81 and r HEMA = 0.92, r MMA = 0.81 respectively. 1 H and 13 C{ 1 H} NMR spectra were analyzed with the help of DEPT, 2D HSQC and 2D TOCSY spectrum. The long range interactions of carbonyl carbon with methoxy protons and oxy methylene carbon with hydroxyl proton were determined with the help of heteronuclear multiple bond coherence (H MBC) spectrum. With the help of 2D spectra it was found that carbonyl, α-methyl and quaternary carbon of HEMA and MMA unit were sensitive to various configurational sequences as in poly(2-hydroxy ethyl methacrylate) and poly(methyl methacrylate). The carbonyl and