Macromolecular antioxidants with highly suppressed leaching to the environment, based on hyperbranched poly(ethyleneimine) carrier with bonded sterically hindered phenol and 2 alkyl compatibilizing groups with various chain length were synthesized and tested for their efficiency in stabilization of polyolefins. The synthesis of the macromolecular antioxidants was carried out by amidation of the amine groups present in poly(ethyleneimine) with various carboxylic acids containing sterically hindered phenol and compatibilizing groups, such as n-butyryl, lauryl or stearyl. The structure of the resulting polymers was analyzed by 1 H NMR and by GPC. The antioxidant content of the samples was determined by UV-Vis spectroscopy. The efficiency of the synthesized antioxidants in thermooxidative stabilization of polypropylene was determined by chemiluminescence. The efficiency in photostabilization of polypropylene and polyethylene was investigated by using FT IR and UV-Vis spectroscopies. It was found that the macromolecular antioxidant which did not contain any compatibilizing groups shows the best stabilizing efficiency in both thermooxidative and photooxidation tests. The extent of extraction of the synthesized macromolecular antioxidants from polypropylene films was investigated as well. Low extent of extraction of the maromolecular antioxidants from the polypropylene films was observed in contrast to the high level of leaching of commercially used low molecular weight phenolic antioxidant. These results indicate the environmental advantage of the investigated poly(ethyleneimine) based macromolecular antioxidants over the widely applied low molecular weight compounds.
Thermooxidative degradation of poly(vinyl chloride) (PVC) is inevitable during processing of PVC. Recycling of this polymer requires reprocessing in most of the cases, and due to the low thermal stability of PVC, it is of paramount importance to reveal the effect of thermooxidation on the thermal stability of this commercially important polymer. However, detailed systematic investigations are lacking on this crucial problem. In this study, the thermal behavior of PVCs thermooxidized in dilute dioctyl phthalate (DOP) (di(2-ethylhexyl) phthalate, DEHP) plasticizer was investigated by DSC, thermal gravimetry and isothermal degradation under inert atmosphere. It was found that thermooxidation leads to PVCs with certain extent of internal plasticization by DOP chemically bound to the PVC chains and by the oxidized chain segments as well. These striking results also indicate that the decreased thermal stability caused by thermooxidation in the course of the primary processing of this polymer should be taken into account in order to efficiently stabilize PVC products for reprocessing and recycling.2
Phthalimide monofunctional hyperbranched polyglycerols (HbPG) were successfully synthesized, for the first time, by applying a new, highly efficient phthalimide/potassium phthalimide (PhthIm/K-PhthIm) initiating system for the anionic ring-opening multibranching polymerization of glycidol. As the analyses of the resulting polymers by UV and NMR spectroscopies, vapor pressure osmometry, aqueous and organic phase GPCs and ESI-MS proved, well-defined HbPGs with one phthalimide moiety, predetermined average molar masses, and narrow molar mass distributions were formed. The phthaloyl group was quantitatively cleaved by hydrazinolysis to form a monoamine functional HbPG. The amine functionality of the HbPG molecules at the initiating site was transformed into carboxylic, maleimide, and chloroacetamide groups. All functionalization reactions were quantitative as proved by multidimensional NMR spectroscopy. These findings indicate that the PhthIm/K-PhthIm combination can be utilized in the polymerization and subsequent derivatizations of other epoxides as well. In addition, the selectively modifiable reactive headgroup can be applied for obtaining various novel functionalized materials.
Ruthenium catalyzed ring closing metathesis (RCM) and ring opening metathesis polymerization (ROMP) reactions using a PIB-supported bis(arylimino)acenaphthene (BIAN) complex has been reported. The BIAN Ru-complex exhibits excellent catalytic activity and tolerates a wide range of substrates at low catalyst loadings. DFT calculations were also carried out on some selected key intermediates in the reaction mechanism to study the effect of having the conjugated aromatic moiety (BIAN ligand) in the backbone of the complex. The newly synthesized PIB-BIAN Ru-complex shows comparable catalytic activities to the commercially available second generation Hoveyda-Grubbs catalyst. The recycled complex was reused for up to eight reaction cycles for the RCM of N,N-diallyl tosylamine affording high average isolated yield.
Poly(ethylene terephthalate) (PET) materials with different molecular weights were isothermally crystallized from melt by systematically varying the temperature and duration of the treatment performed in the differential scanning calorimeter (DSC). Multiple endotherm peaks were observed on the subsequent heating thermograms that were separated from each other on the basis of their melting temperature versus crystallization temperature and melting temperature versus crystallinity function. By this new approach five sub-peak sets were identified and then comprehensively characterised. Wide-Angle X-Ray Diffraction (WAXD) analyses revealed that the identified sub-peak sets do not differ in crystalline forms. By analysing the crystallinity and the melting temperature of the sub-peak sets as a function of crystallization time, crystallization temperature and intrinsic viscosity, it was concluded that below the crystallization temperature of 460 K the sub-peak sets that were formed during primary or secondary crystallization transform partially or completely to a third sub-peak set during the heating run of the measurement, while above this temperature, the sub-peak set formed during primary crystallization gradually transforms to a more stable structure, with higher melting temperature. These formations and transformations are described with mathematically defined parameters as well.
Upper critical solution temperature (UCST)-type thermoresponsive behavior of poly(ethylene glycol)-poly(acrylic acid) (PEG-PAA) and poly(poly(ethylene glycol) methacrylate)-poly(acrylic acid) (PPEGMA-PAA) interpolymer complexes has been observed in isopropanol. For these investigations, PPEGMA and PAA with various average molecular weights have been synthesized by atom transfer radical polymerization. It has been found that both the PEG and PPEGMA have lower cloud point temperatures (T cp ) than its mixed polymer solutions with PAA, whereas PAA does not show such behavior in the investigated temperature range. These findings indicate the reversible formation of interpolymer complexes with variable structure and composition in the solutions of the polymer mixtures in isopropanol. Increasing the ethylene glycol/acrylic acid molar ratio or the molecular weight of either the PAA or the H-acceptor PEG component of the interpolymer complexes increases the UCST-type cloud point temperatures of these interpolymer systems. The polymer-polymer interactions by hydrogen bonds between PAA and PEG or PPEGMA and the correlations between T cp and structural parameters of the components revealed in the course of these investigations may be utilized for exploring well-defined UCST-type material systems for various applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.