Heinrich Gruber

Block copolymers derived from photoreactive 2‐oxazolines, 1. Synthesis and micellization behavior

Amphiphilic block copolymers (BCPs) were synthesized consisting of hydrophilic poly(2-methyl-2-oxazoline) blocks and hydrophobic poly(2-alkyl-2-oxazoline) blocks with undecyl-, phenyl-, and the photopolymerizable cinnamoyl-, 4-azidophenyl-, and diin- moieties. The BCPs were prepared by living cationic ring opening polymerization of the corresponding monomers. The resulting amphiphilic block copolymers show good solubility in water depending on the ratio of hydrophilic to hydrophobic moieties inside the block copolymer as well as the formation of block copolymeric micelles as proven by dynamic light scattering experiments and electron microscopy. The size of the aggregates shows a clear dependence on the polymers molecular weight and the ratio of the hydrophilic to hydrophobic building blocks.

Chemical stability of silicone oil in the human eye after prolonged clinical use

OBJECTIVE To investigate the assumption that silicone oil is chemically stable in the human eye after prolonged clinical use as a vitreous substitute. DESIGN Experimental study. MATERIAL Samples of silicone oil recovered from the vitreous cavities of 25 consecutive patients up to 26 months (mean, 9.2 months) after implantation and 4 different batches of original highly purified silicone oil with a kinematic viscosity of 5000 mPa.s were analyzed. Visible silicone oil emulsification was present in 18 of the 25 eyes. INTERVENTION Gas chromatography/mass spectroscopy (GC/MS) was used to detect and characterize low-molecular weight components (LMWC). Gel permeation chromatography (GPC) was used to determine the molecular weight distribution of the silicone oils. Functional groups of the silicone oils were quantified and characterized by infrared (IR) spectroscopy and 1H nuclear magnetic resonance (1H NMR) spectroscopy. MAIN OUTCOME MEASURES The sample oils explanted from the eyes were compared to the original oils with regard to LMWC, molecular weight distribution, and type and amount of functional groups. RESULTS The GC/MS chromatograms showed no peaks indicative of LMWC in any of the 25 sample oils explanted from the eyes or any of the original oils. In the GPC chromatograms, the peak position occurred at the same retention times with identical signal shape in all original and sample oils, indicating that the molecular weight and the molecular weight distribution did not change after prolonged implantation. The IR spectroscopy and 1H NMR spectroscopy showed characteristic absorption bands at 1260 cm(-1) related to symmetric deformation vibration of the Si-CH3 group and at 800 cm(-1) related to the Si-(CH3)2 group. This was identical for all sample and original oils. CONCLUSIONS Highly purified 5000-mPa.s silicone oils, used as prolonged retinal tamponades in patients with proliferative vitreoretinopathy, proliferative diabetic retinopathy, and tractional retinal detachment after central retinal vein occlusion, are chemically stable in the human eye and do not undergo chemical modification. The LMWC do not play a substantial role in the variations of oil emulsification.

Photoinitiators with Functional Groups. Part I. Polymer Photoinitiators

Abstract A series of new polymerizable photoinitiators (PIs) based on hydroxyalkylphenones has been synthesized by Grignard reaction of 4-vinylphenylmagnesiumchloride with suitable carbonyl compounds. Radical homopolymerization and copolymerization of the PIS with various vinyl monomers yielded polymer PIS compatible with either hydrophilic or hydrophobic resin systems. The PI monomers and polymers are characterized by excellent photoinitiating activity comparable with the most efficient known PIS and exhibit high migration stability.

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.

Photolithographically patternable modified poly(HEMA) hydrogel membrane

SummaryPolymer with pendant methacryloyl group was synthesized by the substitution reaction of poly(2-hydroxyethyl methacrylate) [poly(HEMA)] with methacryloyl chloride. This photocurable polymer was characterized using 1H-NMR and bromine titration, and the results were reasonably well consistent. The photocrosslinking of this modified poly(HEMA) was carried out by the addition of a low molecular weight sensitizer without adding functional monomer and crosslinker. These precursors showed a high photosensitivity. Polymers with a degree of substitution as low as 2 mol-% methacryloyl group could be efficiently crosslinked within few seconds of UV exposure to give water insoluble transparent hydrogel membranes. By irradiation of a film of the photocurable polymer precursor containing lacatate oxidase (LOD), a rather unstable enzyme, the enzyme was gently immobilized by physical entrapment.

Photoinitiators with Functional Groups. Part II. Silicon-Containing Photoinitiators

Abstract The new photoinitiators (PIs) 1-(4-dimethylsilyl)phenyl-2-hydroxy-2-methyl-propan-1-one (8a) and 1-(4-dimethylsilyl)phenyl-2-methoxy-2-methyl-propan-1-one (8b) have been synthesized by Grignard reaction of 4-dimethylsilylphenylmagnesium chloride (5) with protected acetone cyanohydrins. The photoactivity of 8a was similar to the most efficient commercial hydroxyalkylphenone 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur 1173) whereas 8b exhibits even higher efficiency. 8a and 8b were reacted with allyl alcohol, allyl amine, vinyl acetic acid, 3-allyloxypropane-1,2-diol, allyl glycidyl ether, polybutadiene, and a vinyl polysiloxane to yield new functional PIs of high activity. Thus, hydrosilation reactions of the new PIs enable the preparation of a variety of functional derivatives usable in different UV-curable systems.

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.