Interactions of the phospholipid 1,2-dipalmitoylsn-glycero-3-phosphocholine (DPPC) with the amphiphilic diblock copolymer Ch-lPEG 30 -b-hbPG 24 (ChP) are studied at the air-water interface by surface pressure-mean molecular area (π-mmA) measurements of mixed Langmuir films and adsorption measurements of ChP to the air-water interface covered with DPPC monolayers at different initial surface pressure values π 0 . ChP is composed of a single hydrophobic cholesteryl (Ch) moiety covalently bound to a diblock copolymer consisting of a hydrophilic linear poly (ethylene glycol) (lPEG) block and a hydrophilic hyperbranched poly(glycerol) (hbPG) block. Langmuir isotherms and compression moduli of the mixed Langmuir films of different molar ratios reveal distinct interactions between DPPC and ChP during compression. It is demonstrated that the behavior of the DPPC/ChP mixtures is dominated by DPPC up to a molar ratio of 10:1, whereas the behavior is predominantly governed by ChP in mixtures with lower DPPC content (molar ratios of 5:1, 2:1, and 1:1). In adsorption measurements, a strong affinity of ChP to DPPC is observed after injection into the water subphase. The surface pressure value π in up to which ChP is able to penetrate into DPPC monolayers is determined to the remarkably high value of 48.2 mN/m which attests the favorable interactions between DPPC and the Ch moiety of ChP. Atomic force microscopy on LB films of DPPC/ChP mixtures of different molar ratios transferred onto hydrophilic substrates confirms the presence of two different phases, a DPPC-rich phase and a ChP-rich phase.
Poly(ethylene glycol) (PEG) is often used to biocompatibilize surfaces of implantable biomedical devices. Here, block copolymers consisting of PEG and l‐cysteine‐containing poly(amino acid)s (PAA's) were synthesized as polymeric multianchor systems for the covalent attachment to gold surfaces or surfaces decorated with gold nanoparticles. Amino‐terminated PEG was used as macroinitiator in the ring‐opening polymerization, (ROP), of respective amino acid N‐carboxyanhydrides (NCA's) of l‐cysteine (l‐Cys), l‐glutamate (l‐Glu), and l‐lysine (l‐Lys). The resulting block copolymers formed either diblock copolymers, PEG‐b‐p(l‐Glux‐co‐l‐Cysy) or triblock copolymers, PEG‐b‐p(l‐Glu)x‐b‐p(l‐Cys)y. The monomer feed ratio matches the actual copolymer composition, which, together with high yields and a low polydispersity, indicates that the NCA ROP follows a living mechanism. The l‐Cys repeat units act as anchors to the gold surface or the gold nanoparticles and the l‐Glu repeat units act as spacers for the reactive l‐Cys units. Surface analysis by atomic force microscopy revealed that all block copolymers formed homogenous and pin‐hole free surface coatings and the phase separation of mutually immiscible PEG and PAA blocks was observed. A different concept for the biocompatibilization of surfaces was followed when thiol‐terminated p(l‐Lys) homopolymer was first grafted to the surface and then covalently decorated with HOOC‐CH2‐PEG‐b‐p(Bz‐l‐Glu) polymeric micelles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 248–257
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