Synthesis of novel styrene-olefin triblock copolymer via living anionic polymerization

Innovative strides in polymer synthesis have led to the successful living anionic polymerization of styrene-olefin triblock copolymers, yielding varying molecular weights and a remarkably narrow dispersity (Đ) in cyclohexane solvent at 45°C, initiated by n-butyllithium. The novel approach employs anionic polymerization, augmented by the aid of a coupling agent known as 1,12-dibromododecane. Unlike traditional alcohol-based methods employed in polystyrene synthesis, this coupling agent, introduced at the end of the reaction, grafts two living macro-styrene chains with the dodecane chain, effectively acting as the pivotal second component in the formation of the triblock copolymer. Extensive experimentation pinpointed 45°C as the optimal temperature for anionic copolymerization in cyclohexane solvent. The comprehensive analysis, encompassing 13C NMR, 1H NMR, FTIR spectroscopy, and GPC, confirms the successful synthesis of styrene-dodecane-styrene triblock copolymer. The NMR results illustrate successful molecular structures, while GPC attests to the precision, showing a narrow Đ of below 1.2. This pioneering approach not only underscores the efficiency of anionic polymerization in the synthesis of styrene-olefin-styrene triblock copolymer using termination strategy but also promises extensive implications in material science and industrial applications

Effect of Reaction Temperature on Tacticity in Polymerization of Methyl Methacrylate: A Study by Nuclear Magnetic Resonance Spectroscopy

Hypothesis: In the synthesis of vinyl polymers, one of the important parameters that play a significant role in the physical-mechanical properties is the tacticity of monomers within the polymer chain. Polymethyl methacrylate is considered one of the important industrial polymers. The method of its synthesis can have a major effect on this parameter and finally on the final properties. One of the parameters that has a significant effect on the stereoregularity of this polymer is the reaction temperature.Methods: The poly methyl methacrylate was synthesized at three different temperatures of 50, 150, and 250 °C via bulk thermal polymerization method. The most important instrument that can be used to study tacticity order is nuclear magnetic resonance spectroscopy. The tacticity of the polymethyl methacrylate (PMMA) was investigated and studied through alpha-methyl protons splitting and alpha-methyl and carbonyl carbons splitting, respectively, by proton (1HNMR) and carbon (13CNMR) nuclear magnetic resonance spectroscopy in deuterated chloroform (CDCl3) and deuterated tetrahydrofuran (THF-d8). The assignment of all stereosequences at triad level for alpha-methyl proton and pentad level for alpha - methyl carbon and carbonyl carbon were carried out by liquid nuclear magnetic resonance spectroscopy in deuterated chloroform. Bernoullian and first-order Markov statistics models were calculated for the synthesized sample and compared with the experimental results.Findings: The results indicated that probability of meso (Pm) was increased by increasing the methyl methacrylate polymerization temperature. The corresponding probability of meso values determined for synthesized polymethyl methacrylate at 50, 150, and 250°C were 0.203, 0.274, and 0.356, respectively. Finally, the effect of tacticity on glass transition temperature using differential scanning calorimetry (DSC) is discussed. The temperature glassy (Tg) values by DSC results were shown that the synthesized polymethyl methacrylate at 50, 150, and 250°C had 126.0, 125.1 and 102.9 oC, respectively

Microstructural Investigation and MolecularWeight Determination of 1, 2-Polybutadiene by Nuclear Magnetic Resonance Spectroscopy

In this research, the microstructural of low molecular weight 1,2-polybutadiene (1,2-PBD) was conducted by 1H and 13C nuclear magnetic resonance spectroscopy (NMR) to determine the isomeric contents of 1,4-cis, 1,4-trans and 1,2-vinyl in 1,2-PBD polymer structures. Number average molecular weight for low molecular weight 1,2-PBD was measured by NMR techniques and the results were compared with gel permeation chromatography. Due to the presence of methyl end group and its comparison with repeating units in 1,2-PBD microstructure, the number average molecular weight was calculated by NMR techniques. For calculation of surface areas, carbon and protons of methyl groups were characterized using distortion enhancement by polarization transfer (DEPT) methods. For proton assignment of methyl end groups in 1H NMR spectral analysis the heteronuclear multiple quantum coherence (HMQC) method was employed. Finally, stereoregularity and tacticity of 1,2-PBD were investigated through pentad and heptad sequences splitting of olefinic methylene and methine carbons pendant groups with various NMR acquisition temperatures from 20 to 50oC. 13C NMR spectra showed that with increasing of NMR acquisition temperature, the number of split peaks of two olefinic carbons increased

Determination of Polybutadiene Unsaturation Content in Thermal and Thermo-Oxidative Degradation Processes by NMR

The unsaturation content of various polybutadiene (PBD) types of 1,4-cis, 1,4-trans and 1,2-vinyl isomers with different molecular weights was investigated. An important parameter for unsaturation content of polybutadiene would be the determination of olefnic and aliphatic contents for three types of isomers. For this purpose, proton and carbon nuclear magnetic resonance spectroscopy methods were employed for determination of 1,4-cis, 1,4-trans and 1,2-vinyl contents. A change of adjustable parameter of NMR software was made for accurate integrals giving better results. The accuracy in calculation of low molecular weight PBD, surface area of chain end group decreased in aliphatic region. Furthermore, the changing of unsaturation content versus time was considered for 1,2-PBD and 1,4-PBD in thermal degradation conditions at 250°C. NMR results showed that during heating, the unsaturation content decreased for 1,2-PBD and was not changed for 1,4-PBD. In fact, the basic factor responsible for changing of unsaturation content in thermal degradation of PBD may be due to the presence of 1,2-vinyl isomer. Finally, changing in unsaturation content versus time was observed for 1,2-PBD and 1,4-PBD in thermo-oxidative degradation conditions at 100°C. The NMR results showed that at extended time, the unsaturation content decreased for 1,4-PBD and was not changed for 1,2-PBD. Moreover, the basic factor for changes in unsaturation content in thermo-oxidative degradation of PBD is due to the presence of 1,4-cis and 1,4-trans isomers

Vinyl Chloride Emulsion Polymerization Reaction: Effect of Various Formulations

A mixture  of  sodium  lauryl  sulfate  (SLS)  as  ionic  emulsifer  and  stearyl alcohol as non-ionic emulsifer was employed in a vinyl chloride emulsion polymerization  reaction  to  study  the  infuence  of  various  interactive parameters involved in the reaction system. It was found that the particle size was dependent on the amount and type of emulsifer. The average particle size of polyvinyl chloride was dropped by higher amount of emulsifying agents.  At the gel point, more heat was generated by higher amount of vinyl chloride fed into the reaction system. The molecular weight of the polymer was decreased by increases in reaction temperature while,  it  increased by augmenting  the amount of emulsifer. According to the 13C NMR and FTIR spectroscopic data no defect was detected in the chain structure of synthetic polyvinylchloride product. An optimization of polymerization reaction condition was reached based on ultimate particle size desired for its favorable distribution in plastisols

Sample Thickness and Structural Changes in Thermo-Oxidative Degradation of Polybutadiene

The thermo-oxidative degradation of two viscous liquid resins of 1,2- poly-butadiene  (1,2-PBD) and 1,4- polybutadiene  (1,4-PBD) have been studied by differential scanning calorimetry (DSC) and thermogravimetry analy-sis  (TGA). To  study  further,  the  effect of flm  thickness on oxidation kinetics was periodically studied by tracing the weight of the samples to make comparison with DSC results at constant temperature of 100°C under atmospheric pressure. Finally, the structural changes of 1,4-PBD were investigated by carbon-13 nuclear magnetic resonance spectroscopy (13C NMR). The results from 13C NMR from 1,4-PBD show that after heat treatment new carbon peaks are obtained for an epoxide carbon at 58.6 ppm, an adjacent methylene carbon of epoxide group at 24.0 ppm and a peroxide methine carbon group at 86.7 ppm. The results from TGA and DSC studies conclude that 1,2-PBD do not age due to its structure. The results from NMR spectroscopy indicate that besides structural changes, increase in mass is due to radical addition to double bond while, epoxide groups are one of major products of thermal oxidation which can be identifed from their 13 C NMR peaks

Online Morphology Development of Immiscible Polymer Blends in the Presence of an Interfacial Modifier

This study focuses on the online morphology development of a typical immiscible polymer blend subjected to a shear flow field in the presence of the high percentage of an interfacial modifier. The blend components were fluid at room temperature. To follow the details of the morphology development more closely, a drop-in-matrix structure was selected. The matrix and the dispersed phases were polyisobutylene (PIB) and polydimethylsiloxane (PDMS) of various viscosities, respectively. The selected three viscosities of PDMS generated a wide range of viscosity ratios, i.e., 0.04 to 2.3, at room temperature. Both polymers exhibited Newtonian behavior over the investigated shear rate range and no normal forces were observed. The interfacial modifier was a diblock copolymer including PIB and PDMS blocks with close molecular weight. The shear flow field was made using a coaxial cylinders system. The velocity of each cylinder was controlled separately. The results obtained for the blend system in the absence of an interfacial modifier were similar to the observations of previous researchers. A symmetrical breakup was observed for clean drops with the odd number of the resulting breakup droplets. The addition of the interfacial modifier drastically influenced the blend morphology development. The deformation of the compatibilized drops was considerably different from the deformation observed for the corresponding clean counterparts. The breakup was no longer symmetrical and predictable. The viscosity ratio played a determining role in morphology development of the compatibilized drop. The deformation and breakup of the drops at low and high viscosity ratios were not similar. While the low viscosity ratio of the compatibilized drops demonstrated tip-streaming at low shear rates and the high viscosity ratio of the drops showed end-pinching

Kinetic Investigation of Styrene Free Radical Polymerization by Using Binary Mixtures of Monofunctional Initiators

Polymerization of styrene in presence of two monofunctional initiators is studied kinetically in an ampoule scale. Polymerizations were ceased at different conversions for each ampoule while the temperature was increased almost linearly during the reaction. Three different initiator mixtures were used. The first mixtures were composed of benzoil peroxide (BPO) and t-butyl perbenzoate (TBPB) with various molar ratios and temperature programs. The second and third series were performed on mixtures of BPO and α,α'-azobisisobutyronitrile (AIBN) and AIBN with TBPB, respectively. The experimental results for these series revealed thatincreasing the percentage of TBPB in the initiator mixtures at the same reaction temperature intervals enhanced polymerization rate and molecular weight of the resulting polymers. On the other hand the results from the second series indicated that reducing AIBN in the mixture would have reduction effect on the reaction temperatureintervals while both conversion and the polymer molecular weight are increase

Polyaniline-Modified TiO2, a Highly Effective Photo-catalyst for Solid-Phase Photocatalytic Degradation of PVC

A series of polyaniline-modified TiO2 photo-catalysts (TiO2@PANI) were prepared via an in-situ polymerization of aniline onto TiO2 nanoparticles. The Fourier-transform infrared spectroscopy (FT-IR) and thermogravimetric analyses (TGA) confirmed that the polyaniline (PANI) successfully grafted on the TiO2 NPs. The X-ray diffraction (XRD) patterns showed that the crystalline structure of the TiO2 did not change during the preparation of PANI. Photodegradable nanocomposites were prepared by embedding the photocatalysts into the commercial poly(vinyl chloride) (PVC) samples. The nanocomposite films were compared against pure PVC and PVC-TiO2 films for their photodegradation performances. The photocatalytic activity of the TiO2@PANI catalysts improved with an increase in the inorganic/organic molar ratio. With the TiO2 aniline molar ratio of 10, the PVC-TiO2@PANI nanocomposite film lost about 67% of its weight after 720 h irradiation under UV. Meanwhile, the pure PVC and PVC-TiO2 control films lost about 12 and 45% of their initial weights, respectively. Results showed that the rate at which the PVC is photodegraded can be controlled by the amount of the TiO2 NPs as well as the initial TiO2 aniline molar ratio. The SEM micrograms indicated a rougher and more porous surface for the irradiated PVC-TiO2@PANI compared with controls