Aggregation and Crosslinking of Poly(N,N‐dimethylacrylamide)‐b‐pullulan Double Hydrophilic Block Copolymers

The self‐assembly of polymers is a major topic in current polymer chemistry. In here, the self‐assembly of a pullulan based double hydrophilic block copolymer, namely pullulan‐b‐poly(N,N‐dimethylacrylamide)‐co‐poly(diacetone acrylamide) (Pull‐b‐(PDMA‐co‐PDAAM)) is described. The hydrophilic block copolymer induces phase separation at high concentration in aqueous solution. Additionally, the block copolymer displays aggregates at lower concentration, which show a size dependence on concentration. In order to stabilize the aggregates, crosslinking via oxime formation is described, which enables preservation of aggregates at high dilution, in dialysis and in organic solvents. With adequate stability by crosslinking, double hydrophilic block copolymer (DHBC) aggregates open pathways for potential biomedical applications in the future.     

Interaction of N-tert-butylaziridine with π-electron acceptors, 2. Polymerization initiated by tetracyanoethylene

The interaction of N-tert-butylaziridine (TBA) with the strong π-electron acceptor tetracyanoethylene (TCNE) was investigated, which results in ring-opening polymerization of the aziridine. Charge-transfer complex formation between TBA and TCNE was proved by means of UV/VIS spectroscopy and is assumed to be the first stage of the initiation. There is evidence that only linear TBA homopolymers are formed and TCNE is not covalently bound in the polymer chains as comonomer. The acceptor is present in the final products as a stable complex with the nitrogen atoms along the polyaziridine chains.     

Dermatoses in pregnancy

A number of immunological, endocrine, metabolic and vascular changes with various influences on the skin occur in the organism during pregnancy. The specific dermatoses of pregnancy are a heterogenous group of diseases with a different impact on both mother and child. Their clinical characteristics, diagnostic criteria and therapeutic options are discussed in the present review.     

Antigen-specific CD4- and CD8-positive signatures in different phases of Mycobacterium tuberculosis infection

Current diagnostic standards for Mycobacterium tuberculosis (MTB) infection do not distinguish between active and latent tuberculosis (TB). To identify specific biomarkers characterizing the different forms of TB infection, we investigated in parallel with the QuantiFERON -TB Gold In-Tube (QFT-IT) the use of flow cytometry measuring CD4 and CD8 MTB-specific immune response in 17 active-TB patients, 21 health care workers (HCW), 14 recent contacts of TB patients (RC-TB), and 10 bacille Calmette Guerin (BCG)–vaccinated healthy controls (BCG-HC).     

Synthesis of poly(N-tert-butylaziridine)s with functional end-groups

Poly(N-tert-butylaziridine) (poly(TBA)) with hydroxy, amino, HO? C(O)? CH?CH? C(O)? and ? P(O)(OCH₃)₂ end-groups were synthesized via termination reactions of living poly(TBA) with appropriate nucleophiles. 2-Aminoethanol, sodium 2-aminoethylate, maleic anhydride and dimethyl phosphonate were used. The functionally terminated oligomers were of uniform size and with a functionally near one.     

Interaction of N-tert-butylaziridine with π-electron acceptors, 1. Zwitterion copolymerization with maleic anhydride

Zwitterion copolymerization of N-tert-butylaziridine (TBA) with the weak π-electron acceptor maleic anhydride (MA) was investigated. It was demonstrated that the reaction proceeds by opening of both aziridine and anhydride rings, and copoly(ester-amide)s of different composition were prepared depending on the polymerization conditions. On the basis of a model reaction it was assumed that charge-transfer interaction is a stage of the zwitterion mechanism. The structure and the composition of the products obtained were investigated.     

Synthesis of poly(N-tert-butylaziridine) macromonomers and graft copolymers with uniform side chains

Poly(N-tert-butylaziridine) (polyTBA) macromonomers with allylamino-, allyloxy- and methacrylate end-groups were synthesized via deactivation of living polyTBA with appropriate nucleophiles. The macromonomers were copolymerized with N-vinyl-2-pyrrolidone (NVP), 2-hydroxyethyl methacrylate (HEMA) and isoprene (Is). Two types of graft copolymers were obtained: the first one is constituted of hydrophilic backbone (polyNVP or polyHEMA) and hydrophobic uniform polyTBA side chains. The second type is composed of a flexible hydrophobic polyIs backbone and hard hydrophobic polyTBA side chains which, however, become water swellable after quaternization.     

Chromatographic investigations of polyacetals in the critical range of liquid chromatography, 2. Determination of functionality and molecular weight distributions in α,ω-bis(9-anthrylmethylpoly(1,3,6-trioxacyclooctane))s obtained by “active chain-end mechanism”

The fractions obtained by cationic active chain-end polymerization of 1,3,6-trioxacylooctane initiated with (CF₃SO₂)₂O ( I ), CF₃SOOCC₆H₄CO^⊕?O₃SCF₃( II ) and (C₆H₅)₃C^⊕PF ( III ) were investigated using high-performance liquid chromatography (HPLC) at the “critical point” of adsorption. The propagating species were converted into 9-anthrylmethyl groups by suitable reactions of termination of transformation. Their incorporation made the chain ends detectable in the ultraviolet spectrum. The samples were separated at conditions specified for poly(1,3,6-trioxacyclooctane)s (polyTOCs) obtained with (CF₃SO₂)₂O as initiator. The functionality and molecular weight distribution of polyTOCs obtained with mono- and bifunctional initiators and with different counterions were compared and discussed. In the reaction mixtures oligomers of undesired functionality were detected irrespective of the usage of mono- or even bifunctional initiators. A correct method was used to determine the completeness of the separation and to calculate the percentages of the individual fractions. The order of initiators depending on the amount of the undesired end-functionality fractions in the products obtained has been established. Attempts were made to elucidate the reactions complicating the cationic chain-end polymerization of cyclic acetals and leading to a mixture of cyclic, dead, monofunctional and bifunctional oligomers and polymers. The results were summarized and compared with functionality and molecular weight distributions of oligo(1,3,6-trioxacyclooctane)s obtained by “activated monomer mechanism” which have been discussed in the first paper of this series.