Multicompartment micelles from blends of terpolymers

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

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Lonsdale

Whittaker

Monteiro

2009

“…They exhibit switchable amphiphilic characteristics, that is, one hydrophilic segment becomes hydrophobic accompanied by physical or chemical transformations including temperature, pH, and ionic strength, whereas another hydrophilic segment remains soluble in water. [1][2][3][4][5][6][7][8][9][10][11][12] Because of their stimuli responsiveness and easily tunable functionality, DHCs provide a wide range of applications such as drug delivery, 13 gene therapy, 14,15 colloidal stabilization, and as a template for the preparation of nanomaterials, 16,17 and, therefore, DHCs have received great attentions. Typical hydrophilic segments used in DHCs include poly(vinylpyridine), 18,19 poly(acrylic acid), 20,21 poly(ethylene glycol) (PEG), 18,[22][23][24] and polypeptides.…”

mentioning

confidence: 99%

Synthesis of well‐defined pH‐responsive PPEGMEA‐g‐P2VP double hydrophilic graft copolymer via sequential SET‐LRP and ATRP

Zhai

Song

Yang

et al. 2011

A series of well‐defined double hydrophilic graft copolymers containing poly(poly(ethylene glycol) methyl ether acrylate) (PPEGMEA) backbone and poly(2‐vinylpyridine) (P2VP) side chains were synthesized by successive single electron transfer living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET‐LRP of poly(ethylene glycol) methyl ether acrylate (PEGMEA) macromonomer using CuBr/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained homopolymer then reacted with lithium diisopropylamide and 2‐chloropropionyl chloride at −78 °C to afford PPEGMEA‐Cl macroinitiator. poly(poly(ethylene glycol) methyl ether acrylate)‐g‐poly(2‐vinylpyridine) double hydrophilic graft copolymers were finally synthesized by. ATRP of 2‐vinylpyridine initiated by PPEGMEA‐Cl macroinitiator at 25 °C using CuCl/hexamethyldiethylenetriamine as catalytic system via the grafting‐ from strategy. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept relatively narrow (Mw/Mn ≤ 1.40). pH‐Responsive micellization behavior was investigated by 1H NMR, dynamic light scattering, and transmission electron microscopy and this kind of double hydrophilic graft copolymer aggregated to form micelles with P2VP‐core while pH of the aqueous solution was above 5.0. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

“…Such structures-especially when they are amphiphilic in character-find ample applications in selforganizing system ranging from the formation of micellar structures in solution to nanostructured materials in the solid state. [1][2][3][4][5] Not surprisingly, a wide variety of approaches exist to obtain block copolymers including nonradical polymerization routes such as ring opening (metathesis) polymerization (RO(M)P) 6 and ionic polymerization 7 as well as radical routes, most prominently via atom transfer radical polymerization (ATRP), 8,9 nitroxide-mediated polymerization (NMP) [10][11][12][13] as well as the reversible addition fragmentation chain transfer process (RAFT) 14 or reverse iodine transfer polymerization (RITP). 15 The degree of complexity in apply-ing these techniques varies as do the required reaction conditions.…”

Section: Introductionmentioning

confidence: 99%

Formation of triblock copolymers via a tandem enhanced spin capturing—nitroxide‐mediated polymerization reaction sequence

Junkers

Zhang

Wong

et al. 2011

The preparation of ABA‐type block copolymers via tandem enhanced spin capturing polymerization (ESCP) and nitroxide‐mediated polymerization (NMP) processes is explored in‐depth. Midchain alkoxyamine functional polystyrenes (Mn = 6200, 12,500 and 19,900 g mol−1) were chain extended with styrene as well as tert‐butyl acrylate at elevated temperature NMP conditions (T = 110 °C) generating a tandem ESCP‐NMP sequence. Although the chain extensions and thus the block copolymer formation processes function well (yielding in the case of the chain extension with styrene number average molecular weights of up to 20,800 g mol−1 (PDI = 1.22) when the 6200 g mol−1 precursor is used and up to 67,500 g mol−1 (PDI = 1.36) when the 19,900 g mol−1 precursor is used and 21,600 g mol−1 (PDI = 1.17) as well as 37,100 g mol−1 (PDI = 1.21) for the tert‐butyl acrylate chain extensions for the 6200 and 12,500 g mol−1 precursors, respectively), it is also evident that the efficiency of the block copolymer formation process decreases with an increasing chain length of the ESCP precursor macromolecules (i.e., for the 19,900 g mol−1 ESCP precursor no efficient chain extension with tert‐butyl acrylate can be observed). For the polystyrene‐block‐tert‐butyl acrylate‐block‐polystyrene polymers, the molecular weights were determined via triple detection SEC using light scattering and small‐angle X‐ray scattering. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.