Stereochemistry Of Poly Research Articles

Tuning TiO2 suspension stability with poly(α-alkyl carboxylic acids) via side chain length and chain stereochemistry

Effects of hydrophobicity and stereochemistry of poly(α-alkyl carboxylic acids) on the properties of TiO2 suspensions were studied with experimental and in silico methods. Zeta potential measurements show that the addition of the more hydrophilic poly(acrylic acid) (PAA) to TiO2 suspensions shifts the isoelectric point of the nanoparticles towards lower pH the most, followed by poly(methacrylic acid) (PMA) and poly(ethacrylic) acid (PEA). Stereochemistry has a less pronounced effect on suspension stability, except at low pH, where isotactic PMA (iPMA) is not soluble in water. Dynamic light scattering measurements show that the aggregate size of the nanoparticles correlates well with their zeta potential and the aggregates are largest at the isoelectric point of the nanoparticles. Molecular dynamics (MD) and Monte Carlo (MC) computer simulations were used to study the interaction of polyacids with the surface of nanoparticles. MD simulations show that PAA forms the largest amount of hydrogen bonds with TiO2, followed by PMA. PEA forms very low numbers of hydrogen bonds with the nanoparticle surface. MC simulations were used to study the effect of pKa of COOH groups of polyacids on their adsorption on TiO2. It was found that even small differences in pKa between the polyacids have a strong effect.

Branched Poly(lactide) Synthesized by Enzymatic Polymerization: Effects of Molecular Branches and Stereochemistry on Enzymatic Degradation and Alkaline Hydrolysis

In this article the effects of the number of molecular branches (chain ends) and the stereochemistry of poly(lactide)s (PLAs) on the enzymatic degradation and alkaline hydrolysis are studied. Various linear and branched PLAs were synthesized using lipase PS (Pseudomonas fluorescens)-catalyzed ring-opening polymerization (ROP) of lactide monomers having different stereochemistries (L-lactide, D-lactide, and D,L-lactide). Five different alcohols were used as initiators for the ROP, and the monomer-to-initiator molar feed ratio was varied from 10 to 100 and 1000 for each branch in the polymer architecture. The properties of branched PLAs that would affect the enzymatic and alkaline degradations, i.e., the glass transition temperature, the melting temperature, the melting enthalpy, and the advancing contact angle, were determined. The PLA films were degraded using proteinase K or 1.0 M NaOH solution, and the weight loss and changes in the number average molecular weight (Mn) of the polymer were studied during 12 h of degradation. The results suggest that an increase in the number of molecular branches of branched PLAs enhances its enzymatic degradability and alkali hydrolyzability. Moreover, the change in Mn of the branched poly(L-lactide) (PLLA) by alkaline hydrolysis indicated that the decrease in Mn was in the first place dependent on the number of molecular branches and thereafter on the length of the molecular branch of branched PLA. The branched PLLA, poly(D-lactide) (PDLA), and poly(D,L-lactide) (PDLLA) differed in weight loss and change in Mn of the PLA segment during the enzymatic degradation. It is suggested that the branched PDLLA was degraded preferentially by proteinase K.

Copolymerization of N-vinyl phthalamide with acrylate and methacrylate monomers and preliminary analysis of the stereochemistry of poly(N-vinyl phthalamide)

N-Vinyl phthalamide was copolymerized with methyl methacrylate, isobutyl methacrylate or butyl acrylate. The copolymerizations were initiated free radically and it was necessary to conduct the polymerizations in solution or else insoluble products would result. In most cases the polymerizations preceded to relatively high conversions in a short time. The conversions necessitated the use of high conversion methods to calculate the reactivity ratios. The N-vinyl phthalamide was found to be the less reactive monomer in all cases. As part of this study, poly(N-vinyl phthalamide) homopolymer was synthesized by free radical initiation. While the 1H-NMR spectrum yield very little information concerning polymer stereochemistry, the methine carbon resonance in the 13C-NMR spectrum displayed a sensitivity to polymer stereochemistry.

Stereochemistry of poly(1,3-cyclohexadienes). NMR investigation of effects due to the solvent medium and to the mechanism of polymerization

Stereochemistry of poly(1,3-cyclohexadienes). NMR investigation of effects due to the solvent medium and to the mechanism of polymerization

The chemistry and the stereochemistry of poly( N-alkyliminoalanes) : XIV. Some advances in the synthesis of mixed poly( N-alkylimino) derivatives of aluminum and alkaline-earth metals

Crystalline mixed imino derivatives of aluminum and calcium, [(t-C 4H 9NAlH) 3(t-C 4H 9NCa · 3THF)] or magnesium [(t-C 4H 9AlH) 3(t-C 4H 9NMg · THF)] were obtained by the reaction of a mixture of Ca(AlH 4) 2— or Mg(AlH 4) 2—tetrahydrofuranate and AlH 3 · N(CH 3) 3 with t-C 4H 9NH 2. The molecular structures of these compounds have been fully characterized by X-ray analysis of single crystals. A mixed imino derivative of composition [(t-C 4H 9NAlH) 3(t-C 4H 9NMg · 3THF)] was also obtained by direct synthesis from aluminum, magnesium and t-C 4H 9NH 2 in tetrahydrofuran under hydrogen pressure.

ChemInform Abstract: THE CHEMISTRY AND STEREOCHEMISTRY OF POLY‐(N‐ALKYLIMINOALANES) PART 6, A NOVEL SYNTHESIS OF POLY‐(N‐ALKYLIMINOALANES) BY REACTION OF ALKALI METAL ALANATES WITH PRIMARY AMINES

Chemischer InformationsdienstVolume 6, Issue 33 Organoelement Compounds ChemInform Abstract: THE CHEMISTRY AND STEREOCHEMISTRY OF POLY-(N-ALKYLIMINOALANES) PART 6, A NOVEL SYNTHESIS OF POLY-(N-ALKYLIMINOALANES) BY REACTION OF ALKALI METAL ALANATES WITH PRIMARY AMINES S. CUCINELLA, S. CUCINELLASearch for more papers by this authorG. DOZZI, G. DOZZISearch for more papers by this authorA. MAZZEI, A. MAZZEISearch for more papers by this authorT. SALVATORI, T. SALVATORISearch for more papers by this author S. CUCINELLA, S. CUCINELLASearch for more papers by this authorG. DOZZI, G. DOZZISearch for more papers by this authorA. MAZZEI, A. MAZZEISearch for more papers by this authorT. SALVATORI, T. SALVATORISearch for more papers by this author First published: August 19, 1975 https://doi.org/10.1002/chin.197533304Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue33August 19, 1975 RelatedInformation

ChemInform Abstract: THE CHEMISTRY AND THE STEREOCHEMISTRY OF POLY(N‐ALKYLIMINOALANES) PART 5, THE PREPARATION AND CRYSTAL STRUCTURE OF THE PENTAMER ((HALN‐I‐PR)2(H2ALNH‐I‐PR)3)

Chemischer InformationsdienstVolume 6, Issue 28 Organoelement Compounds ChemInform Abstract: THE CHEMISTRY AND THE STEREOCHEMISTRY OF POLY(N-ALKYLIMINOALANES) PART 5, THE PREPARATION AND CRYSTAL STRUCTURE OF THE PENTAMER ((HALN-I-PR)2(H2ALNH-I-PR)3) G. PEREGO, G. PEREGOSearch for more papers by this authorG. DEL PIERO, G. DEL PIEROSearch for more papers by this authorM. CESARI, M. CESARISearch for more papers by this authorA. ZAZZETTA, A. ZAZZETTASearch for more papers by this authorG. DOZZI, G. DOZZISearch for more papers by this author G. PEREGO, G. PEREGOSearch for more papers by this authorG. DEL PIERO, G. DEL PIEROSearch for more papers by this authorM. CESARI, M. CESARISearch for more papers by this authorA. ZAZZETTA, A. ZAZZETTASearch for more papers by this authorG. DOZZI, G. DOZZISearch for more papers by this author First published: July 15, 1975 https://doi.org/10.1002/chin.197528352Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue28July 15, 1975 RelatedInformation

The chemistry and the stereochemistry of poly( N-alkyliminoalanes) : VI. A novel synthesis of poly( N-alkyliminoalanes) by reaction of alkali metal alanates with primary amines

A novel synthesis of poly( N-alkyliminoalanes) (PIA) is reported. This involves the reaction in hydrocarbon solvents of LiAlH 4 or NaAlH 4 with primary amines having a nitrogen with α- or β- secondary carbon atoms or with tertbutylamine. Complexes of iminoalanes with alkali metal hydrides are obtained from linear amines. The same reaction carried out in polar solvents always gives complexes of PIA with LiH or NaH and the solvent. This new synthesis is simpler and convenient for producing soluble and well characterized PIA, some of which are not obtainable by other methods.

The chemistry and the stereochemistry of poly( N-alkyl-iminoalanes) : I. Synthesis and physicochemical characterization of poly( N-alkyliminoalanes)

The structural features of poly( N-alkyliminoalanes) (PIA) and their dependence on the method of preparation as well as on the amine have been investigated. Different PIA have been synthesized from ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl and cyclohexylamine, and have been characterized by X-ray diffraction, mass spectrometry, 1H and 13 C NMR. In general all the results agree with the formation of oligomers of-HAlNR-units, with three dimensional structures made up by four and six membered rings. In particular a cage structure has been found for (HAlN- iso-C 3H 7) 6 by X-ray diffraction on a single crystal.