narrow temperature range of ~4 K above T C and prohibits the release of molecules
that are incorporated in the polymer aggregate. In large mesoglobules, formed at low
heating rates and at high polymer concentrations, a considerable amount of water is
entrapped and a microphase separates from the collapsed polymer chains at high
temperatures. This results in aggregates possessing an aqueous core and a corona
consisting of collapsed polymer chains. Fast heating rates, low polymer concentrations, and hydrophobic subunits in the polymer make the entrapment of water less
favorable and lead to a higher degree of vitrification. This has obvious consequences
for the design and use of thermoresponsive polymeric systems in the fast growing
field of drug delivery.
Following A. D. Schlu ¨ter’s question of “whether one can create a molecular object,
i.e., a molecular system that does not respond to its surrounding, by making a polymer
thicker and thicker” [93], shape-persistent dendronized polymers in solution were
studied by advanced pulse EPR methods. As expected, DEER spectroscopy yields the
size (thickness) of different generations of charged cylindrical dendronized polymers
in solution [94]. Moreover, a combination of CW EPR and a modified isotopologspecific DEER variant provides a better understanding of how amphiphilic molecules
can be loaded into and released upon external stimulation from these thick
polymers [95].
4 Functional Materials
Macromolecular and supramolecular systems are becoming increasingly important as
functional materials in various applications, e.g., ion conductors [96], sensors [97],
and organic electronics [98]. In all cases, magnetic resonance provides unprecedented
details of structure and dynamics [99–104]. Moreover, applications for synthetic
polymers in medicine are emerging [105]. Research at the interface of polymer
chemistry and the biomedical sciences has given rise to the first nanosized
(5–100 nm) polymer-based pharmaceuticals, the “polymer therapeutics.” Polymer
therapeutics include rationally designed macromolecular drugs, polymer–drug and
polymer–protein conjugates, polymeric micelles containing covalently bound drug,
and polyplexes for DNA delivery. Another important route for generating
nanoparticles and controlling their interaction with cells is provided by miniemulsion
polymerization [106], which can also be used to encapsulate, e.g., magnetic contrast
agents for magnetic resonance imaging (MRI) [107].
4.1 Elastin-Like Polypeptides and Drug Delivery
Drug release can, of course, also be realized using building blocks from nature. In
this respect, elastin-like polypeptides (ELPs) are particularly interesting [51]. ELPs
are genetically encoded polymers composed of repeats of the amino acid VPGXG
Probing Macromolecular and Supramolecular Structure, Dynamics, and Function. . .
309
that are incorporated in the polymer aggregate. In large mesoglobules, formed at low
heating rates and at high polymer concentrations, a considerable amount of water is
entrapped and a microphase separates from the collapsed polymer chains at high
temperatures. This results in aggregates possessing an aqueous core and a corona
consisting of collapsed polymer chains. Fast heating rates, low polymer concentrations, and hydrophobic subunits in the polymer make the entrapment of water less
favorable and lead to a higher degree of vitrification. This has obvious consequences
for the design and use of thermoresponsive polymeric systems in the fast growing
field of drug delivery.
Following A. D. Schlu ¨ter’s question of “whether one can create a molecular object,
i.e., a molecular system that does not respond to its surrounding, by making a polymer
thicker and thicker” [93], shape-persistent dendronized polymers in solution were
studied by advanced pulse EPR methods. As expected, DEER spectroscopy yields the
size (thickness) of different generations of charged cylindrical dendronized polymers
in solution [94]. Moreover, a combination of CW EPR and a modified isotopologspecific DEER variant provides a better understanding of how amphiphilic molecules
can be loaded into and released upon external stimulation from these thick
polymers [95].
4 Functional Materials
Macromolecular and supramolecular systems are becoming increasingly important as
functional materials in various applications, e.g., ion conductors [96], sensors [97],
and organic electronics [98]. In all cases, magnetic resonance provides unprecedented
details of structure and dynamics [99–104]. Moreover, applications for synthetic
polymers in medicine are emerging [105]. Research at the interface of polymer
chemistry and the biomedical sciences has given rise to the first nanosized
(5–100 nm) polymer-based pharmaceuticals, the “polymer therapeutics.” Polymer
therapeutics include rationally designed macromolecular drugs, polymer–drug and
polymer–protein conjugates, polymeric micelles containing covalently bound drug,
and polyplexes for DNA delivery. Another important route for generating
nanoparticles and controlling their interaction with cells is provided by miniemulsion
polymerization [106], which can also be used to encapsulate, e.g., magnetic contrast
agents for magnetic resonance imaging (MRI) [107].
4.1 Elastin-Like Polypeptides and Drug Delivery
Drug release can, of course, also be realized using building blocks from nature. In
this respect, elastin-like polypeptides (ELPs) are particularly interesting [51]. ELPs
are genetically encoded polymers composed of repeats of the amino acid VPGXG
Probing Macromolecular and Supramolecular Structure, Dynamics, and Function. . .
309