Olefin polymerization and copolymerization
Mohammad Reza Jozaghkar; Farshid Ziaee
Abstract
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 ...
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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.
Composites and nanocomposites
Hamed NazarpourFard
Abstract
Polyvinylpyrrolidone (PVP) composites based on rice husk (RH), rice husk carbon (RHC, i.e., black rice husk ash (BRHA)) and rice husk ash (RHA, i.e., white rice husk ash (WRHA)) were prepared separately through solution casting method. Similar composites were made using polystyrene (PS) through the same ...
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Polyvinylpyrrolidone (PVP) composites based on rice husk (RH), rice husk carbon (RHC, i.e., black rice husk ash (BRHA)) and rice husk ash (RHA, i.e., white rice husk ash (WRHA)) were prepared separately through solution casting method. Similar composites were made using polystyrene (PS) through the same protocol. The carbon and ash obtained from this type of rice husk were obtained via pyrolysis at 300 and 600 °C, respectively, for 1 hour. The effects of these additives on the spectroscopic characteristics of polymers were verified by examining the infrared (FT-IR) and X-ray diffraction (XRD) spectra of the prepared composites. The resulting showed a remarkable difference between the spectra of parent polymers and the corresponding composites. Changes in peak width and 2θ parameters (observed in XRD patterns) revealed that PVP possesses better interactions with RHC, while PS has better interactions with RHA. Due to the high hydrophilicity of PVP, some investigations were accomplished on the hydrophilic properties of PVP samples. Polystyrene did not reveal detectable water vapor absorption (WVA), thus this experiment was not carried out for PS samples. Eventually, it was disclosed that there are significant discrepancies between the hydrophilic properties of PVP and its composites. In the other word, the WVA decreased from 290% for parent PVP to 210% for PVP-RHC composite.
Olefin polymerization and copolymerization
Mojtaba Farrokhi; Mahdi Abdollahi
Abstract
Polystyrene (PSt) has been known as one of the important polymers with a wide range of applications. Ability to synthesize PSt with different but predictable molecular weights for various applications is very important in the laboratories and industries. In this study, using various simple and inexpensive ...
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Polystyrene (PSt) has been known as one of the important polymers with a wide range of applications. Ability to synthesize PSt with different but predictable molecular weights for various applications is very important in the laboratories and industries. In this study, using various simple and inexpensive techniques with only free radical mechanism, it was tried to synthesize PSt with different low (< 2×104 g mol-1) to high (> 105 g mol-1) molecular weights. PSts with high and moderate molecular weights (2×104-105 g mol-1) were synthesized using thermal and conventional free radical polymerizations, respectively. Reverse iodine transfer radical polymerization (RITP) was utilized to synthesize PSt with a low and controlled molecular weight. Conversion, molecular weight distribution and PSt structure were analyzed using 1H-NMR spectroscopy and size exclusion chromatography (SEC), respectively. Moreover, ω-iodo poly(dimethylsiloxane), i.e. PDMS-I, was also used as a macrotransfer agent for ITP of styrene. Diblock copolymer of PDMS-b-PSt was characterized by 1H-NMR and SEC analyses.
