Biomedical subjects

Søren Hvilsted

Publications and source records attributed to Søren Hvilsted.

3 recordsLinked to original sources

PubMed2005

Photodimerization in pyrimidine-substituted dipeptides.

Ten N(epsilon)-glycylornithineamide derivatives have been synthesized containing various N(alpha)-linked pyrimidine-1-ylacetyl groups which can undergo (2pi + 2pi) photodimerization on irradiation with UV light at 254 nm. The dimerization efficiency of the free and bound pyrimidine groups was compared in aqueous solution: it was dependent on the substitution of the pyrimidine ring. N(alpha),N(alpha')-bis-(uracil-1-ylacetyl)-(N(epsilon)-glycylornithineamide) and N(alpha),N(alpha')-bis-(5-bromouracil-1-ylacetyl)-(N(epsilon)-glycylornithineamide) were identified as possible candidates for optical data storage.

Acetates↗

PubMed2003

Photoinduced anisotropy in a family of amorphous azobenzene polyesters for optical storage.

We investigate parameters associated with optical data storage in a variety of amorphous side-chain azobenzene-containing polyesters denoted as E1aX. The polyesters possess a common cyano-substituted azobenzene chromophore as a side chain, but differ in their main-chain polyester composition. Seventeen different polymers from the E1aX family divided into four classes, depending on the type of the main-chain substituent (one-, two-, and three-ring aromatic or alicyclic) have been thoroughly investigated. Various parameters characterizing the photoinduced birefringence in these materials, such as the response time, thermal and light stability, and long-term stability under ambient light at room temperature have been measured. Each of these parameters is quantitatively represented and therefore it is possible to make a clear comparison between the properties of the polymers. The results indicate that the long-term stability at ambient temperature is closely related to the thermal stability of the photoinduced birefringence. A strong correlation has also been found between the response time and the stability of the induced anisotropy toward illumination with unpolarized white light. One of the classes of E1aX polymers characterized by two-ring aromatic substituent in the main chain is a good candidate for optical data storage media. A recording energy of approximately 2 J/cm2 is sufficient to induce high refractive-index modulations of deltan = 0.13 in these materials, which is retained even at elevated temperatures (>130 degrees C). Long-term stability of greater than one year for the induced anisotropy has also been achieved.

Journal Article↗

PubMedDate not supplied

Modification of jute fibers with polystyrene via atom transfer radical polymerization.

Atom transfer radical polymerization (ATRP) was investigated as a method of covalently bonding polystyrene to jute (Corchorus capsularis) and as a possible approach to fiber composites with enhanced properties. Jute fibers were modified with a brominated initiator and subsequently ATRP modified to attach polystyrene and then examined using SEM, DSC, TGA, FTIR, XPS, elemental analysis, and Py-GC-MS. These techniques confirmed that polystyrene had been covalently bound to the fibers and consequently ATRP-modified jute fiber mats were used to prepare hot-pressed polystyrene composites. Composite specimens were tensile tested and fracture surfaces examined using SEM. Although SEM examination suggested different fracture modes between unmodified fiber and ATRP-modified samples, the tensile strength of modified samples was slightly lower on average than that of unmodified samples. For fiber composite applications, we conclude that further optimization of the ATRP method is required, possibly targeting higher and more uniform loading of polystyrene on the fibers.

Biocompatible Materials↗