Like most of the materials used by humans, polymeric materials are proposed in the literature and occasionally exploited clinically, as such, as devices or as part of devices, by surgeons, dentists, and pharmacists to treat traumata and diseases. Applications have in common the fact that polymers function in contact with animal and human cells, tissues, and/or organs. More recently, people have realized that polymers that are used as plastics in packaging, as colloidal suspension in paints, and under many other forms in the environment, are also in contact with living systems and raise problems related to sustainability, delivery of chemicals or pollutants, and elimination of wastes. These problems are basically comparable to those found in therapy. Last but not least, biotechnology and renewable resources are regarded as attractive sources of polymers. In all cases, water, ions, biopolymers, cells, and tissues are involved. Polymer scientists, therapists, biologists, and ecologists should thus use the same terminology to reflect similar properties, phenomena, and mechanisms. Of particular interest is the domain of the so-called "degradable or biodegradable polymers" that are aimed at providing materials with specific time-limited applications in medicine and in the environment where the respect of living systems, the elimination, and/or the bio-recycling are mandatory, at least ideally.

Summary: The n‐hexylamine‐initiated polymerization of Nε‐trifluoroacetyl‐L‐lysine N‐carboxyanhydride in N,N‐dimethyformamide was studied by nonaqueous capillary electrophoresis. A polypeptide with a broad molecular weight distribution was obtained and side reactions were clearly identified for polymerization at room temperature. The possibility of living polymerization at 0 °C was demonstrated.Synthesis of living polypeptides by primary amine initiated polymerization of NCA at low temperatures.imageSynthesis of living polypeptides by primary amine initiated polymerization of NCA at low temperatures.

No abstract

Poly(Nepsilon-trifluoroacetyl-L-lysine) was used as a model solute to investigate the potential of nonaqueous capillary electrophoresis (NACE) for the characterization of synthetic organic polymers. The information obtained by NACE was compared to that derived from size exclusion chromatography (SEC) experiments, and the two techniques were found to be complimentary for polymer characterization. On one hand, NACE permitted (i) the separation of oligomers according to their molar mass and (ii) the separation of the polymers according to the nature of the end groups. On the other hand, SEC experiments were used for the characterization of the molar mass distribution for higher molar masses. Due to the tendency of the solutes (polypeptides) to adsorb onto the fused-silica capillary wall, careful attention was paid to the rinsing procedure of the capillary between runs in order to keep the capillary surface clean. For that purpose, the use of electrophoretic desorption under denaturating conditions was very effective. Optimization of the separation was performed by studying (i) the influence of the proportion of methanol in a methanoVacetonitrile mixture and (ii) the influence of acetic acid concentration in the background electrolyte. Highly resolved separation of the oligomers (up to a degree of polymerization n of approximately 50) was obtained by adding trifluoroacetic acid to the electrolyte. Important information concerning the polymer conformations could be obtained from the mobility data. Two different plots relating the effective mobility data to the degree of polymerization were proposed for monitoring the changes in polymer conformations as a function of the number of monomers.

Polymerizations of Nε‐trifluoroacetyl‐L‐lysine N‐carboxyanhydride initiated by hexylamine were performed in N,N‐dimethylformamide with different monomer to initiator ratios and at different temperatures. Poly(Nε‐trifluoroacetyl‐L‐lysine) samples were characterized by size exclusion chromatography coupled with multi‐angle laser light detection (SEC‐MALLS) and capillary electrophoresis (CE). If SEC‐MALLS analysis emphasizes the double distribution in molecular weight, nonaqueous CE (NACE) brings additional quantitative information on the oligomeric distribution and on the distribution according to polymer functionality (end‐groups). At room temperature, two termination reactions were clearly identified for these polymerizations. The suppression of these side reactions is reported upon decreasing the reaction temperature to 0 °C. A strong reduction of the bimodal aspect of the molecular weight distribution was obtained with the addition of urea to the polymerization medium. The possibility of a living and controlled polymerization at 0 °C with urea was demonstrated and illustrated by the synthesis of two block copolypeptides.magnified image

Poly(L‐lactic acid) sheets, prepared by melt extrusion, were treated with O2−, He−, and N2−plasmas generated in radio frequency (RF) at 13.56 MHz. Atmospheric pressure discharge at 20 kHz in helium was also applied to the modification of the sheets. The surface of the PLLA sheets was etched to form the characteristic morphology, and the patterns were different depending on the type of plasma. Polar groups composed of –COOH and –OH were incorporated by plasma treatment, and the surface became wettable. Surface modification became effective after a short treatment period, e.g., 30 seconds. Receding contact angles (θr) changed remarkably, and the surface properties were closely related to the increase in the surface energy of the polar contribution (γsp). Biodegradation of the poly(L‐lactic acid) sheets was not enhanced practically, even though the surface became hydrophilic after plasma treatment.

The structure of stereoregular polymers of 1,3‐pentadiene was determined by 13C‐NMR spectroscopy at 22.6 MHz. Not only was it possible to distinguish between cis‐1,4 and trans‐1,4 but also between isotactic and syndiotactic cis‐1,4 structures. Triad effects were detected in the trans‐1,2 syndiotactic polypentadiene; 1,4–1,2 as well as 1,4–4,1 linkages were observed.

No abstract