Search results for "Plastics"

Water-soluble hyperbranched polyglycerol photosensitizer for enhanced photodynamic therapy

2020

Porphyrin and its derivatives as promising photosensitizers have been widely utilized in photodynamic therapy (PDT). However, the water-solubility and biocompatibility of porphyrins are the typical bottlenecks in clinical PDT processes. Herein, we successfully fabricated a new type of water-soluble, hyperbranched polyglycerol photosensitizer through one-step esterification between water-soluble hyperbranched polyglycerol (hbPG) and fluorophenylporphyrin (FP). Compared with the linear control polymer, i.e., FP covalently connected with linear polyethylene glycol (LPEG), the hyperbranched structures bearing multiple porphyrin units generated more singlet oxygen and exhibited higher cytotoxici…

Patterning of a Surface Immobilized ATRP Initiator with an Inkjet Printer

2010

A new technique for patterning polymer brushes on the micrometer scale has been developed in which an inkjet printer was used to deposit droplets of acid on a surface-immobilized initiator for atom transfer radical polymerization (ATRP). The acid cleaved an ester bond in the ATRP initiator in a saponification reaction. As a result, the ATRP initiator was rendered inactive. To control the degree of defunctionalization, a new initiator containing a weak ester bond was derived from a tertiary alcohol. Comparison to an established ATRP initiator, derived from a primary alcohol, showed that the novel initiator was defunctionalized with a higher efficiency. Control of the reaction time allowed to…

Molecular Weight Distribution of Hyperbranched Polymers Generated by Self-Condensing Vinyl Polymerization in Presence of a Multifunctional Initiator

1999

The molecular weight distribution (MWD) is derived for polymers generated by self-condensing vinyl polymerization (SCVP) of a monomer having a vinyl and an initiator group (“inimer”) in the presence of a multifunctional initiator. If the monomer is added slowly to the initiator solution (semi-batch process), this leads to hyperbranched polymers with a multifunctional core. If monomer and initiator are mixed simultaneously (batch process), even at vinyl group conversions as high as 99%, the total MWD consists of polymers which have grown via reactions between inimer molecules (i.e., the normal SCVP process) and those which have reacted with the initiator. Consequently, the weight distributio…

Oligoethyleneoxide spacer groups in polymerizable surfactants

1991

Cationic and zwitterionic polymerizable surfactants bearing tri- and tetraethyleneglycol spacer groups between the polymerizable moiety and the surfactant structure were prepared and polymerized. Monomers and polymers were investigated with respect to their aggregation behavior in aqueous systems and compared to analogous monomers and polymers lacking spacer groups. In the case of the monomeric surfactants, the spacer groups depress both the Kraffttemperature and the critical micelle concentration. the area occupied per molecule at the air-water interface is substantially enlarged by the spacers, whereas the depression of surface tension is nearly constant. Although the monomers with and wi…

Melt stabilization of wet polyamide 6

2002

Abstract Melt processing of polycondensate polymers must be carried out after careful drying in order to avoid any hydrolytic chain scission caused by the presence of water or other small molecules. In this work, the effect of two different antioxidants on the processing and flow properties of a polyamide 6 sample not dried before processing operations has been studied. One of these stabilizers seems to protect the wet polymer from hydrolytic chain scission. This action has been interpreted considering that the stabilizer hydrolyses instead of the polyamide macromolecules.

Poly-l-Lysine-Poly[HPMA] Block Copolymers Obtained by RAFT Polymerization as Polyplex-Transfection Reagents with Minimal Toxicity

2015

Herein we describe the synthesis of poly-L-lysine-b-poly[N-(2-hydroxypropyl)-metha-crylamide)] (poly[HPMA]) block copolymers by combination of solid phase peptide synthesis or polymerization of α-amino acid-N-carboxy-anhydrides (NCA-polymerization) with the reversible addition-fragmentation chain transfer polymerization (RAFT). In the presence of p-DNA, these polymers form polyplex micelles with a size of 100-200 nm in diameter (monitored by SDS-PAGE and FCS). Primary in vitro studies with HEK-293T cells reveal their cellular uptake (FACS studies and CLSM) and proof successful transfection with efficiencies depending on the length of polylysine. Moreover, these polyplexes display minimal to…

Homogeneous mixtures of polybetaines with low molecular weight salts

1996

The prepaparation of amorphous, homogeneous blends of zwitterionic polymers with various low molecular weight salts, and in particular with ionic dyes was studied. Homogeneous miscibility was achieved in many cases up to equimolar amounts of salt, even for bulky compounds. Whether miscibility is achieved, or not, depends in a subtle way on the chemical structure of the salt, but no obvious correlation between structure and miscibility could yet be revealed. Spectral shifts of the dye UV/Vis spectra in solution as well as in bulk suggest strong interactions between the polybetaines and the admired salts.

Crystallization of polymer melts under fast cooling. II. High-purity iPP

1992

SYNOPSIS Samples of a high-purity isotactic polypropylene (iPP) were quenched from the melt so as to monitor cooling history. A continuous variation of morphology and crystal structure was obtained with cooling rate. This is discussed in relation to sample thermal history evidencing that cooling history relevant to quenched samples is in the neighborhood of 90°C. In particular the samples are essentially mesomorphic when at this temperature cooling rates larger than 80°C/s were adopted, while below a few tens of °C/s only a­ monocline form is obtained. Densities of quenched samples were compared with predictions of an isokinetic extrapolation of Avrami model of polymer crystallization kinet…

Synthesis and radical polymerization of novel methacrylates with mesoionic 6-oxo-1,6-dihydropyrimidin-3-ium-4-olates as photosensitive components

2001

New polymerizable mesoionic 6-oxo-1,6-dihydropyrimidin-3-ium-4-olates 5a-f have been synthesized using tosylated 2-hydroxymethyl methacrylate and various thioureas and malonic acids. Radical polymerization of the mesoionic derivatives 5a, c, d, e with AIBN as initiator resulted in soluble polymers, which were used for the preparation of photosensitive films.

1981

Theoretical predictions from a non-linear model based on the free volume concept, which were previously tested only with a molten polymer, are presented and compared with literature data of solid polyethylene. The agreement is good both when a steady state is reached in the experimentally explored times and when, on the contrary, the data do not show it. Theoretische Berechnungen des elektrischen Verhaltens von Polymeren anhand eines nichtlinearen Modells, die auf dem Konzept des freien Volumens basieren und bisher lediglich an einem geschmolzenen Polymer getestet wurden, werden vorgestellt und mit Literaturdaten von festem Polyethylen verglichen. Die Ubereinstimmung ist gut, wenn in den ex…