Simone Knaus

Synthesis and properties of anionic cellulose ethers: influence of functional groups and molecular weight on flowability of concrete

Abstract The suitability of anionic cellulose ethers as superplasticizers and the effect of chemical structure on the fluidity of cement mixtures was investigated. To elucidate the influence of molecular weight and degree of cellulose backbone substitution, cellulose and hydroxyethyl cellulose with molecular weights

Synthesis, characterization and properties of methylaminocellulose

Homogeneously prepared tosylcelluloses (TC) with degrees of substitution (DS) of DSTos 0.1–1.8 were used as intermediates for the synthesis of methylaminocelluloses (MAC) by nucleophilic substitution with methylamine. TC with DSTos up to 1.1 were shown to be valuable intermediates for selective synthesis of MAC with DSMA varying from 0.1 to approximately 1. No nucleophilic substitution was observed at higher DSTos. At the chosen reaction conditions (60 °C, 48 h) residual tosyl moieties remained unchanged and little hydrolysis took place. The samples obtained were characterized by means of elemental analysis, FTIR and 13C CP/MAS NMR spectroscopy. 13C CP/MAS NMR spectroscopy was found to be an efficient tool for quantification of DSMA. Furthermore, the swelling behaviour in water was investigated and preliminary tests concerning the bilirubin adsorption capacity of MAC were carried out.

Carbohydrate modified photoinitiators

SummariesAs a result of the new trend concerning the development of water-borne UV curable coatings, attention has moved to the synthesis and investigation of water-soluble photoinitiators (Pls). New Pls were synthesized by covalent bonding of carbohydrates such as D-glucose, cellobiose and 1-amino-D-sorbitol to Type I and Type II Pls based on α-hydroxyolkylphenones, thioxonthones and benzophenones.In addition, results of investigations concerning the properties of the Pls such as residual unsaturation, gel content, pendulum hardness and the photoinitiating activity in various water-borne systems are presented.ZusammenfassungDurch den immer grösser werdenden Anteil on wasserverdünnbaren Systemen für die UV-Strahlenhärtung wurden auch zahlreiche wasserlösliche Photoinitiatoren speziell für solche Systeme entwickelt.In dieser Arbeit wurden einige solcher Initiatoren durch kovalente Verknüpfung von Kohlenhydraten wie z.B. Glucose, Cellobiose und Glucomin mit Photoinitiotoren vom Typ I & II z.B. Hydroxyalkylphenonen, Thioxonthonen und Benzophenonen hergestellt.Zusätzlich werden die Aktivitäten und Eigenschaften dieser Photoinitiatoren in verschiedenen wasserbasierenden Harzsystemen präsentiert (z.B. Photo-DSC, Gelgehalt, Restdoppelbindungsgeholt, Pendelhärte usw.)RésuméPar suite de la nouvelle tendance à l’égard du développement des revêtements hydrosolubles et durcissobles par royons-UV, l’attention s’est tournée vers la synthèse et l’investigation des photointioteurs hydrosolubles (Pls). Des nouveoux Pls ont été synthésisés ofin de créer des liasons covalentes des hydrates de carbone tels que I-glucose, cellobiose et l-amino-d-sorbitol avec des photoinitiateurs du Type I et du Type II à base de α-hydroxyalkylsphénones, thioxanthones et benzo phénones. En plus, on présente les resultats des investigations à l’égard des caractéristiques des photoinitiateurs telles que l’insaturation residuelle, la teneur en gel, la dureté pendulaire et leur activite photoinitiatrice en divers systèmes hydrodiluables.

Synthesis and 13C CP MAS NMR spectroscopy of cellulose-graft-poly(N-acetylethylenimine)

Starting from homogeneously prepared tosyl celluloses with DS Tos values ranging from 0.2 to 1.8 poly(N-acetylethylenimine) was grafted onto the cellulose backbone. Tosyl moieties served as starting centers for the living ring opening polymerization using 2-methyl-1,3-oxazoline as the monomeric unit. The grafted products could be characterized by IR and 13 C CP MAS NMR spectroscopy clearly indicating the loss of tosyl moieties as well as the occurrence of the N-acetylethylenimine residues. 13 C CP MAS NMR spectroscopy was also found to be an efficient tool for the quantification of grafted polymer after determination of the relaxation behavior of the various nuclei. Thus the grafting efficiency could be controlled by the DS Tos of the starting tosyl celluloses, whereas the amount of monomers showed only a minor influence on the grafting density.

CARBOHYDRATE MODIFIED POLYDIMETHYLSILOXANES. PART 1. SYNTHESIS AND CHARACTERIZATION OF CARBOHYDRATE SILANE AND SILOXANE BUILDING BLOCKS

A series of silanes containing carbohydrate residues usable as building blocks for the preparation of modified poly(dimethylsiloxane)s (PDMS) were synthesized. Allyl glycosides, allyl ethers and allyl amides of glucose, gluconic acid and glucuronic acid-γ-lactone with protected hydroxyl groups were reacted with diisopropoxymethylsilane in the presence of hydrosilylation catalysts yielding sugar substituted dialkoxysilanes. In addition, di- and trialkoxysilanes containing sugar residues were obtained by reaction of D(+)glucono-δ-lactone with 3-aminopropylsilanes. By hydrosilylation of tetramethylcyclotetrasiloxane with trimethylsilyl (TMS)-protected 3-O-allylglucose a glucose substituted cyclosiloxane was obtained and used in equilibration reactions for the synthesis of water soluble PDMS with pendant sugar moieties. However, the ring double bond of cellobial was found to be unaccessible for hydrosilylations.

Synthesis of sugar-containing hydrophilic porous polymer supports via suspension polymerization

Using different porogens and crosslinkers for 3-O-methacryloyl-1,2;5,6-di-O-isopropylidene-α-D-glucofuranose, porous polymer beads having surface areas of up to 300 m 2 g -1 were synthesized by suspension polymerization. After subsequent removal of the protecting groups, a hydrophilic sugar-containing resin was obtained. In the case when the initial polymer had only very small pores, after hydrolysis, an almost non-porous resin was recovered. With initially large pores, the pore structure of the resin remained unchanged. For resins with medium pore sizes, the pore volume and surface area of the unprotected resin were dependent of the degree of hydrolysis. In fact a linear relationship between surface area and degree of hydrolysis could be observed. Furthermore, this relationship was reversible, i.e. after reprotection of partly or fully hydrolyzed resins, the original pore structure of the protected polymer could be recovered. Depending on the degree of hydrolysis, porous resins of various hydrophilicity, containing reactive hydroxyl groups suitable for further derivatization have been synthesized.

Surface and bulk modification of polyolefins by functional aryl nitrenes as highly reactive intermediates

Aromatic azides with hindered amine light stabilizer (HALS) residues or hydrophilic groups such as glucose, sucrose and dextrine residues were synthesized and used for surface modification of polyolefins. By UV-irradiation nitrenes were formed, which are able to react with polyolefin surfaces. By photochemical immobilization of the carbohydrates hydrophilicity of PE and PP was strongly increased (surface tensions > 44mN/m). Light stability of PP surfaces modified with HALS azides was comparable with PP, stabilised with Tinuvin 770. Bulk modification of ethylene-propylene and ethylene-octene copolymers was achieved by grafting nitrenes formed by thermal decomposition of azido benzoic acid. In a circulating air oven up to 1.55 wt% amino benzoic acid residues could be bonded covalently to ethylene-propylene-copolymers, less than half of it to ethylene-octene-copolymers. Reactive extrusion resulted in grafting yields of more than 50% for both types of copolymers.

Photoinitiators with Functional Groups. Part IV. Water-Soluble Photoinitiators Containing Quaternary Ammonium Groups

Abstract The syntheses and properties of a series of new water-soluble hydroxyalkylphenone-based photoinitiators (PIs) for UV curing of water-borne systems is described. By reaction of tosyl- (2), chloro- (3), and dimethylamino- (4) derivatives of the commercially available PI 2-hydroxy-1-[4-(2-hydroxy-ethoxy)phenyl]-2-methylpropan-1-one (1, Darocur 2959) with tertiary amines and halogenides, respectively, PIs containing quaternary ammonium groups exhibiting high water solubility were obtained. Preliminary photocalorimetric tests of the activity demonstrated excellent efficiencies for the PIs in a commercial water-based acrylate formulation, exceeding the photoactivity of the reference PI (1) substantially.

Grafting of functional maleimides onto oligo- and polyolefins

In this paper the modification of polyolefins, especially polypropylene (PP), with maleimides is discussed. As there are many problems associated with the analysis of the grafting reaction, commercially available squalane and eicosane were used as model compounds for ethylene-propylene-copolymer (EPR) and polyethylene (PE). 2,4,6,8-Tetramethylnonane (TMN) was synthesized as a novel model compound for PP. N-Phenylmaleimide and maleimido benzoic acid were grafted onto the oligomers in solution using 2,5-dimethyl-2,5-di-(tert-butyl-peroxy)-3-hexyne (Luperox 130) as radical initiator. The grafting efficiency was determined by NMR-, UV-spectroscopy, gravimetry and gas-chromatography. The influence of several reaction parameters on homopolymerformation, amount of modified oligomer and grafting efficiency could be elaborated. NMR-spectroscopy and SEC were used to analyse the nature of the grafts. Grafting yields were almost quantitative using up to more than 10 mol% monomer, but dropped at higher monomer concentrations to about 60%. The amount of modified oligomer could be increased with higher monomer concentrations or reaction temperatures. Grafting of polymers was done by reactive extrusion. Products were analysed by IR-spectroscopy. Optimal grafting yields could be achieved with 1 wt% monomer and 0.5 wt% peroxide concentration.

Exact determination of the degree of substitution of high molar mass hyaluronan by controlling the conformation in solution

The purpose of the present study was the development of an accurate method to determine the degree of substitution (DS) of modified hyaluronic acid (HA) by proton nuclear magnetic resonance (1H NMR) spectroscopy. The influence of the effect of ionic strength and pH on 1H NMR spectra of HA was studied. The results showed a correlation between the conformation of HA in solution and the quality of the 1H NMR spectra. The best spectra with full proton mobility are obtained when HA is dissolved in D2O with 2 M NaCl or D2O with 0.1 M NaOD with a maximum concentration of 5 mg/ml. Under those conditions the size of the polymer coils is reduced below the concentration of chain overlap point, all the protons show the same response and a correct degree of substitution can be determined.