Helmut Schlaad

Synthesis of nearly monodisperse polystyrene–polypeptide block copolymers via polymerisation of N-carboxyanhydrides

Primary amine hydrochlorides promote a well-controlled ring-opening polymerisation of Z-L-lysine-N-carboxyanhydride in DMF at 40-80 degrees C; the polystyrene-poly(Z-L-lysine) block copolymers synthesised exhibit a very narrow molecular weight distribution, close to a Poisson distribution.

pH-Responsive Bioactive Glycopolypeptides with Enhanced Helicity and Solubility in Aqueous Solution

Copolypeptides of L-glutamate and glucosylated L-/DL-allyl- or DL-propargylglycine were synthesized by ring-opening polymerization and thiol-ene/yne photochemistry in aqueous solution, allowing the mild introduction of sugar units (here, glucose) in the final step. The glucosylated and non-glucosylated samples adopt a random-coil conformation in neutral and basic media and an α-helical conformation in acidic media, the helical content depending on the number and configuration of allyl-/propargylglycine units. The glucocopolypeptides unveil enhanced helical stability and solubility down to pH 3.5. Turbidity assays proved the selective binding of the polymers to the plant lectin concanavalin A.

A versatile polypeptoid platform based on N-allyl glycine

N-Allyl glycine N-carboxyanhydride (NCA) was synthesized and polymerized by ring opening polymerization under homo- or heterophase conditions to afford well-defined polypeptoids (M(W) = 1.5-10.5 kg mol(-1), PDI = 1.1-1.4). Poly(N-allyl glycine) demonstrated stimuli-responsive behaviour in water and was readily modified via thiol-ene photochemistry under experimentally benign conditions.

Solid-state morphologies of linear and bottlebrush-shaped polystyrene-poly(Z-L-lysine) block copolymers

Abstract The solid-state structures of polystyrene–poly(Z- l -lysine) block copolymers were examined with respect to the polymer architecture and the secondary structure of the polypeptide using circular dichroism, quantitative small- and wide-angle X-ray scattering, and electron microscopy. Linear block copolymers exhibit a hexagonal-in-lamellar structure where folded and packed polypeptide α-helices form lamellae which extend over an exceptional broad range of the composition diagram. Star- or bottlebrush-shaped copolymers are able to stabilize a larger interface area than linear ones which promotes the formation of undulated lamellar mesophases. Depending on the secondary structure of polypeptide segments, plane lamellar, superundulated lamellar, or corrugated lamellar phases are formed. These results indicate the importance of a secondary structure and packing of polymer chains for the formation of new phases and ordering far from the ‘classical’ phase behavior.

Biohybrid and Peptide-Based Polymer Vesicles

This review covers the major processes and mechanisms involved in the production of biohybrid or peptide-based polymer vesicles by self-assembly. The formation of vesicles conventionally occurs based on geometric packing issues, and becomes predominant when the membrane-forming segment is stiffened due to hydrogen bonding and secondary structure interactions or supramolecular complexation. The vesicles are used for applications in life science, for the purpose of drug/gene delivery, cell surface recognition, and as bioreactors, and for the production of composite materials.

Glycopolymer vesicles with an asymmetric membrane

Direct dissolution of glycosylated polybutadiene-poly(ethylene oxide) block copolymers can lead to the spontaneous formation of vesicles or membranes, which on the outside are coated with glucose and on the inside with poly(ethylene oxide).

Thermoresponsive poly(2-oxazoline)s, polypeptoids, and polypeptides

This review covers the recent advances in the emerging field of thermoresponsive polyamides or polymeric amides, i.e., poly(2-oxazoline)s, polypeptoids, and polypeptides, with a specific focus on structure–thermoresponsive property relationships, self-assembly, and applications.

Aqueous Self-Assembly of Purely Hydrophilic Block Copolymers into Giant Vesicles

Self-assembly of macromolecules is fundamental to life itself, and historically, these systems have been primitively mimicked by the development of amphiphilic systems, driven by the hydrophobic effect. Herein, we demonstrate that self-assembly of purely hydrophilic systems can be readily achieved with similar ease and success. We have synthesized double hydrophilic block copolymers from polysaccharides and poly(ethylene oxide) or poly(sarcosine) to yield high molar mass diblock copolymers through oxime chemistry. These hydrophilic materials can easily assemble into nanosized (<500 nm) and microsized (>5 μm) polymeric vesicles depending on concentration and diblock composition. Because of the solely hydrophilic nature of these materials, we expect them to be extraordinarily water permeable systems that would be well suited for use as cellular mimics.

Quantitative analysis of broad molecular weight distributions obtained by matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry

In order to quantify the error of matrix-assisted laser desorption ionisation (MALDI) time-of-flight (TOF) mass spectrometry in the determination of broad molecular weight distributions, different mixtures by weight of two poly(methyl methacrylate) standards were prepared. These mixtures, with well-defined bimodal molecular weight distributions were analysed by MALDI-TOF mass spectrometry using different matrices (2,4,6-trihydroxyacetophenone and 2,5-dihydroxybenzoic acid) and different cations (Li+, Na+, K+, Rb+ and Cs+) for doping the analyte. From the MALDI-TOF mass spectrometric data, the weight fractions of the two polymers of all mixtures were determined and compared to the values measured by size-exclusion chromatography. The results show that it is possible to obtain the correct Mn and Mw values with 2,5-dihydroxybenzoic acid as matrix and K+ as cationisation metal.

Poly(α-Peptoid)s Revisited: Synthesis, Properties, and Use as Biomaterial.

Polypeptoids have been of great interest in the polymer science community since the early half of the last century; however, they had been basically forgotten materials until the last decades in which they have enjoyed an exciting revival. In this mini-review, we focus on the recent developments in polypeptoid chemistry, with particular focus on polymers synthesized by the ring-opening polymerization (ROP) of amino acid N-carboxyanhydrides (NCAs). Specifically, we will review traditional monomer synthesis (such as Leuchs, Katchalski, and Kricheldorf) and recent advances in polymerization methods to yield both linear, cyclic, and functional polymers, solution and bulk thermal properties, and preliminary results on the use of polypeptoids as biomaterials (i.e immunogenicity, biodistribution, degradability, and drug delivery).