Self‐assembly of well‐defined amphiphilic polymeric miktoarm stars, dendrons, and dendrimers in water: The effect of architecture

Abstract

Five polymeric architectures with a systematic increase in architectural complexity were synthesized by “click” reactions from a toolbox of functional linear polymers and small molecule linkers. The amphiphilic architectures ranged from a simple 3‐miktoarm star block copolymer to the more complex third generation dendrimer‐like block copolymer, consisting of polystyrene (PSTY) and polyacrylic acid (PAA). Micellization of these architectures in water at a pH of 7 under identical ionic strength gave spherical micelles ranging in size from 9 to 30 nm. Subsequent calculations of the PSTY core density, average surface area per PAA arm on the corona‐core interface, and the relative stretching of the PAA arms provided insights into the effect of architecture on the self‐assembly processes. A particular trend was observed that with increased architectural complexity the hydrodynamic diameter, radius of the core in the dry state and the aggregation number also increased with the exception of the third generation dendrimer. On the basis of these observations, we postulate that thermodynamic factors controlling self‐assembly were the entropic penalty of forming PSTY loops in the core counterbalanced by the reduction in repulsive forces through chain stretching. This results in a greater number of aggregating unimers and consequently larger micelle sizes. The junction points within the architecture also play an important role in controlling the self‐assembly process. The G3 dendrimer showed results contradictory to the aforementioned trend. We believe that the self‐assembly process of this architecture was dominated by the increased attractive forces due to stretching of the PSTY core chains to form a more compact core. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6292–6303, 2009

Prognostic significance of immunophenotypic and karyotypic features of Philadelphia positive B‐lymphoblastic leukemia in the era of tyrosine kinase inhibitors

“…However, TEM images of the micelles showed that the particles were smaller than that found by DLS, which is consistent with the literature 49. That may be because the diameter measured by TEM was representative of the dry PS core and collapsed PIL corona state of the micelles,50 and the size by DLS measurement was contributed by the corona stretching in solution.…”

Self-assembling systems: Mining a rich vein

“…water comes to the probe rather than the probe to the water). (2) Looping might indeed occur with 1 and 2, but it is abnormal, which is to say that conventional surfactants with methyl group termini do not act similarly. Although one could argue that if our innocuous acetylene probe was not trustworthy, then all that literature work with huge polar probes would be even more suspect, we preferred to accept probe ambiguity as an annoying fact of life.…”

“…The synthesis and examination of new self-assembling compounds have drawn international attention, as illustrated here via an incomplete and arbitrary listing: Argentina (amphiphilic cyclodextrins) [1]; Australia (amphiphilic dendrimers) [2]; Brazil (sugar-based surfactants) [3]; Canada (amphiphilic copolymers) [4]; China (chiral surfactants) [5]; France (noncovalent amphiphiles) [6]; Germany (bolaamphiphiles) [7]; India (multiple-headgroup surfactants) [8]; Italy (gemini surfactants) [9]; Iran (cleavable surfactants) [10]; Japan (p-electronic amphiphiles) [11]; Korea (T-shaped amphiphiles) [12]; The Netherlands (carbohydrate-based gemini surfactants) [13]; Portugal (amino acid-based amphiphiles) [14]; Spain (urea-based surfactants) [15]; Sweden (heterogemini surfactants) [16]; United Kingdom (light-sensitive surfactants) [17]; and United States (redox-active surfactants) [18].…”

“…True, dealing with self-assemblies (call them ''colloidal particles" if you prefer) exacerbates experimental and theoretical difficulties, but herein lies a challenge, not a disadvantage. (2) Since almost every analytical method known to man has been applied to self-assemblies, research in the area can be a broadly educational experience. Consider, for example, the various methods available to students in a European colloid laboratory with which one of us (FMM) was associated for many years: organic synthesis; theoretical modeling; tensiometry; reflectometry; cryo-TEM; dynamic surface tension; PGSE-NMR, SAXS, SANS, AFM, QCM, TRFQ, SAM, ellipsometry, rheology, and enzyme kinetics.…”

Synthesis of Dendrimer-Like Polymers

“…Along this line, the "click" chemistry between alkyne and azide groups was applied as a coupling reaction in the synthesis of dendrimer-like star polymers. As shown in Scheme 21, combination of copper wire catalyzed "click" chemistry, ATRP of styrene or acrylates, and the transformation of alkylbromide terminus into azido end group led to the formation of miktoarm dendrimer-like star polymers [65][66][67]. Three-arm star polymer bearing three azido termini derived from alkylbromides was coupled with AB-type diblock copolymers with alkyne groups at the junction to yield dendrimer-like miktoarm star terpolymers [68].…”