Five linear amphiphilic multiblock copolymers based on 2-(dimethylamino)ethyl methacrylate (“D”) and methyl methacrylate (“M”), bearing from two to six blocks, were synthesized using sequential group transfer polymerization. All copolymers were obtained from the same polymerization flask (by the withdrawal of a sufficient amount of sample and appropriate adjustment of subsequent monomer loadings) to ensure better comparison between the various multiblocks. A theoretical degree of polymerization (DPth) of 20 was targeted for all D blocks, whereas a DPth of 10 was aimed for the M blocks. Upon characterization using gel permeation chromatography and 1H NMR spectroscopy, the copolymers were confirmed to have the expected values of molecular weights and compositions. Subsequently, the aqueous micellization behavior of these copolymers was probed using dye solubilization, dynamic light scattering, and small-angle neutron scattering. Dye solubilization experiments indicated that micelles readily formed at low copolymer concentrations equal to or less than 0.03% w/w. The scattering measurements revealed that despite the differences in their overall DPth values, the triblock, the tetrablock, and the pentablock copolymers self-assembled in water to form micelles with radii of gyration and hydrodynamic radii very similar to each other, suggesting chain looping and the formation of flowerlike micelles, which is in agreement with recent Monte Carlo simulations.

Four linear amphiphilic multiblock copolymers based on 2-(dimethylamino)ethyl methacrylate (DMAEMA, hydrophilic) and methyl methacrylate (MMA, hydrophobic), bearing from two to five blocks, were synthesized using reversible addition-fragmentation chain transfer polymerization and stepwise monomer additions. The degree of polymerization of each hydrophilic polyDMAEMA block was ∼50, while that of the hydrophobic polyMMA blocks was ca. 20. The stepwise monomer addition procedure secured that each higher multiblock was composed of its immediately lower homologue plus exactly one extra block. The molecular weights (MW) of the synthesized (co)polymers, as measured by gel permeation chromatography (GPC), were close to the theoretically expected. GPC also indicated rather narrow molecular weight distributions which, however, broadened with the number of blocks. The compositions of the copolymers, as determined by proton nuclear magnetic resonance spectroscopy, were also close to the expected values. The cloud points of the copolymers, measured by turbidimetry, were found to increase with the number of blocks. The sizes of the micelles formed by the copolymers in aqueous solution were characterized using dynamic light scattering and small-angle neutron scattering. The determined values of the hydrodynamic radii, the radii of gyration, and the aggregation numbers of the micelles increased slightly with the block number from the triblock to the pentablock copolymer, implying extensive folding of the chains of the tetrablock and the pentablock copolymers in their micelles. The aggregation number of the tetrablock copolymer was approximately one-half that of the diblock copolymer whose unimer MW was onehalf that of the tetrablock, suggesting that the micellar cores of these two types of micelles were composed of the same number of hydrophobic units.

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An amphiphilic cationic polyelectrolyte based on poly[2-(dimethylamino)ethyl methacrylate] (polyDMA) and poly(n-butyl methacrylate) (polyBuMA) with a BuMA–DMA–BuMA–DMA–BuMA–DMA–BuMA heptablock copolymer architecture was studied in aqueous media. This copolymer was found to form a physical hydrogel via the intermolecular hydrophobic association (physical cross-linking) of the BuMA blocks. The rheological properties of the heptablock hydrogels were investigated as a function of copolymer concentration, and pH. The results showed a peculiar pH-dependence of the rheological properties, remarkably different from those observed with associative telechelic polyelectrolytes. Aqueous solutions of this copolymer were free-flowing sols at low pH (below 2) and high pH (above 8), whereas they turned into gels at intermediate pH values. The rheological properties studied as a function of pH showed two additional stiff–soft–stiff gel transitions at pH 4.5 and 6.5. Small-angle neutron scattering revealed the formation of a 3D transient network of bridged flower-like micelles whose structural characteristics, i.e., micellar radius, hard-sphere radius and hard-sphere volume fraction, were smoothly evolving with the pD.

Amphiphilic conetworks based on end‐linked copolymers of the hydrophilic ionizable 2‐(dimethylamino)ethyl methacrylate and the hydrophobic n‐butyl methacrylate bearing 3, 5, 7, and 9 blocks were synthesized using group transfer polymerization, and employing a bifunctional initiator and sequential addition of monomers and ethylene glycol dimethacrylate cross‐linker. All the linear precursors to the conetworks had the same molecular weight and composition, and differed only in their number of blocks. The aqueous degrees of swelling of the ionized conetworks increased with the number of blocks, manifesting the reduction of the driving force for nanophase separation, resulting from the reduction of the length of the hydrophobic segments. Reduction in the tendency for nanophase separation with increasing block number was also supported by atomic force microscopy on bulk conetworks, which indicated a decrease in the domain size as the number of blocks increased.