A series of novel water-soluble amphiphilic triblock copolymers having ABA architecture has been synthesized via atom transfer radical polymerization (ATRP) technique. The blocks comprised a thermoresponsive poly(propylene oxide) (PPO) middle block with a molar mass of around 2000 g·mol-1 and two hydroxy-functional poly(2,3-dihydroxypropyl methacrylate) (also named poly(glycerol monomethacrylate) (PGMA)) outer blocks with lengths varying from 14 to 221 monomeric units per block, which account for the solubility in water. Gel permeation chromatography analysis confirmed unimodal molar mass distributions with polydispersity indexes ranging between 1.29 and 1.40. Their association behavior in aqueous solutions was studied. The size of the micelles formed and the thermal dependence of the micellization process were followed by dynamic light scattering at different temperatures. Depending on the length of the PGMA blocks, micelles showed an average hydrodynamic diameter in the range from 20 to 30 nm. Critical micellization concentrations (cmc) were determined using surface tension measurements, fluorescent probe technique with pyrene as probe molecule and isothermal titration calorimetry and were found to be in the range from 8 × 10-6 to 2 × 10-4 M depending on the length of the PGMA block and on the method used.

Novel water-soluble amphiphilic triblock copolymers poly(glycerol monomethacrylate)-b-poly(propylene oxide)-b-poly(glycerol monomethacrylate) (PGMA-b-PPO-b-PGMA) were synthesized because of their expected enhanced ability to interact with biological membranes compared to the well-known poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-b-PPO-b-PEO) block copolymers. Their bulkier hydrophilic PGMA blocks might induce a disturbance in the packing of liquid-crystalline lipid bilayers in addition to the effect caused by the hydrophobic PPO block alone. To gain a better insight into the polymer-membrane interactions at the molecular level, the adsorption kinetics and concomitant interactions of (PGMA14)(2-)PPO(34) with model membranes of dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) were monitored using infrared reflection absorption spectroscopy (IRRAS) coupled with Brewster angle microscopy (BAM) and surface pressure (pi) measurements. The maximum penetration surface pressure of ca. 39 mN/m suggests that (PGMA14)(2-)PPO(34) is able to insert into lipid monolayers even above the so-called monolayer-bilayer equivalent pressure of 30-35 mN/m. Copolymer adsorption to a liquid-expanded DPPC-d62 monolayer proceeds in a two-step mechanism: (i) initially only the more hydrophobic PPO middle block penetrates the lipid monolayer; (ii) following the liquid-expanded-liquid-condensed (LE-LC) phase transition, the bulky PGMA hydrophilic blocks are dragged into the headgroup region as the PPO block inserts further into the fatty acid region. The adsorption kinetics is considerably faster for DMPC-d54 monolayers due to their higher fluidity. Copolymer adsorption to an LC-DPPC-d62 monolayer leads to a change in the monolayer packing by forcing the lipid alkyl chains into a more vertical orientation, their tilt angle with respect to the surface normal being reduced from initially 30 degrees +/- 3 degrees to 18 degrees +/- 3 degrees. BAM images rule out macroscopic phase separation and show that coalescence of DPPC-d62 LC domains takes place at relatively low surface pressures of pi > or = 23 mN/m, suggesting that (PGMA14)(2-)PPO (34) partitions into both LE as well as LC domains.

ATRP using poly(propylene oxide) monofunctional macroinitiator was carried out with solketal methacrylate (SMA) and the non‐reactive PPO having two N3 terminal groups was removed by dissolution in an excess of n‐hexane. The resulting azido terminated AB diblock copolymer was ‘clicked’ with an α‐alkyne fluorinated compound, followed by acid hydrolysis of the SMA units, a triphilic ABC triblock copolymer was prepared. ATRP of SMA with a difunctional PPO macroinitiator to give ABA triblock copolymer was also carried out. The terminal Br was again exchanged with N3, ‘clicked’ with the α‐alkyne fluorinated compound and likewise hydrolyzed to give a triphilic CABAC pentablock copolymer, i.e., hydrophilic, oleophilic, and fluorophilic blocks were combined.magnified image

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The fate of poly(vinyl alcohol) (PVA, 195,000 g/mol) was studied in rabbits and nude mice after intraperitoneal (i.p.) administration. In-vivo fluorescence imaging using nude mice allowed for studies of tetramethylrhodamine labeled PVA distribution in the body and tracking the urinary excretion. The excreted PVA was studied in detail after collecting the urine of rabbits over a time period of 28 days. The PVA was separated from the urine by dialysis and analyzed by FTIR spectroscopy, (1)H-NMR spectroscopy, and size exclusion chromatography (SEC). Even after extensive dialysis, it was found that the excreted PVA showed a characteristic brownish color. The spectroscopic techniques revealed that this color was caused by the urine pigment (a metabolite of bilirubin) that could not be separated completely from the PVA. SEC showed unambiguously that the PVA with the very high molar mass had a glomerular permeability in the kidneys. Simultaneously, histological studies of the kidneys and the liver demonstrated that the tissues did not show any obvious damage.