Direct synthesis of anisotropic polymer nanoparticles

DOI: 10.1002/anie.200703348

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Angewandte Chemie - International Edition p. 9243 - 9247 (2007)

Update date:2022-09-26

Topics:

Authors:

He, Tao He, Tao

Adams, Dave J.

Butler, Michael F.

Chert, Tse Yeoh

Cooper, Andrew I.

Rannard, Steven P.

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Article abstract of DOI:10.1002/anie.200703348

(Figure Presented) No (self-)assembly required: Both spherical and anisotropic dumbbell polymer nanoparticles with targeted shapes in the < 100-nm size range were prepared by direct synthesis not relying on self-assembly. Atom-transfer polymerization techniques at high concentrations produce both spherical and dumbbell-like nanoparticles directly from simple vinyl monomers on a multigram scale.

Full text of DOI:10.1002/anie.200703348

Angewandte

Chemie

DOI: 10.1002/anie.200703348

Polymer Nanostructures

Direct Synthesis of Anisotropic Polymer Nanoparticles**

Tao He, Dave J. Adams, Michael F. Butler, Chert Tse Yeoh, Andrew I. Cooper,* and

Steven P. Rannard*

The production of materials with control over structure on the

nanometer scale is of fundamental importance in science and

technology. Here we demonstrate the direct synthesis of

polymer nanoparticles with targeted shapes in the size range

< 100 nm, without requiring functional groups to induce self-

assembly. This one-pot route can be scaled up since it uses

conventional polymerization techniques and reagents at high

concentrations to synthesize both spherical and anisotropic

“dumbbell-like” nanoparticles directly from simple vinyl

monomers.

There are few nonbiological examples of the direct

chemical synthesis of complex, nonspherical organic nano-

structures.^[1]There has been much interest in the indirect

formation of nanostructures by cooperative molecular assem-

bly of presynthesized macromolecular building blocks. For

example, certain amphiphilic blockcopolymers self-assemble

to form blockcopolymer micelles or vesicles, which may then

be chemically transformed into static, shell-cross-linked

spherical^[2–7]and toroidal^[8]nanostructures (typical diameters

< 100 nm).^[9]Alternatively, linear triblockrod-coil amphi-

philes with incompatible blocks may form mushroom-shaped

aggregates with dimensions of 8 nm by 2 nm which can stack

to generate supramolecular plate and tape structures.^[10]

Controlled radical polymerization^[11–13]has been used to

produce linear blockcopolymers which self-assemble into

nanomaterials. Recently, conventional^[14–16]and con-

trolled^[17–20]radical polymerization was also used to produce

soluble, high molar mass, branched homopolymers in single-

pot procedures. In this study, we synthesize complex polymer

nanostructures using a one-pot atom-transfer radical poly-

merization^[11](ATRP) approach, avoiding separate self-

assembly and chemical-fixation steps.

copolymer nanoparticles were then synthesized by a con-

trolled branching strategy (Figure 1). In the presence of a

bifunctional monomer, ethyleneglycoldimethacrylate

(EGDMA 4; 0.9:1 ratio relative to initiator 1), the growing

hydrophobic poly(nBuMA) blocks were able to branch and

form chemical bonds between other growing poly(nBuMA)

blocks, hence building a structure composed of covalently

linked copolymer chains (Figure 1). The ratio of branching

bifunctional monomer units to the growing macromolecule

chain is restricted to less than one branched monomer per

chain, and thus the formation of a typical macromolecular

networkis inhibited ^[16]and discrete soluble molecular species

are formed (Figure 1B), in a similar fashion to star polymers

of lower molar mass which have been formed by the “arm

first” ATRP method.^[23–26]Dialysis was used to remove the

THF along with any residual monomer, initiator, or catalyst

and to generate a clear, homogeneous aqueous solution in

which the internal hydrophobic branched poly(nBuMA)

blocks form a collapsed nanoparticle core (Figure 1B).

When more EGDMA was used (1.3:1 ratio of 4/1), microgel

fractions formed and the resultant aqueous solutions were

cloudy rather than clear after dialysis.

TEM investigation of the dialyzed sample revealed

individual, spherical nanoparticles with a mean particle

diameter of 43.2 nm (Figure 2B; see Figure S9 in the

Supporting Information). These particles are generally sim-

ilar in size to those reported for shell-cross-linked micelles,^[2–7]

but, importantly, they have been synthesized in a single

reaction sequence rather than by assembly and cross-linking

of preformed polymers. The polymerizations were conducted

at 35% w/v solids as opposed to the typically low concen-

trations used for the formation of shell-cross-linked

micelles.^[2–7]Analysis of the aqueous solutions formed after

dialysis by dynamic light scattering (DLS) (Figure 2C)

showed a narrowed size distribution with a z-average particle

diameter of 32.5 nm (polydispersity index (PDI) = 0.097).

This diameter is somewhat smaller than the mean diameter

estimated by AFM analysis (40–50 nm; see the Supporting

Information) and by TEM (43.2 nm; see Figure S10 in the

Supporting Information), probably because of spreading on

the TEM/mica surfaces. The overall size distributions are,

however, similar (see Figure 2C,D). By contrast, irregular

filmlike structures with large (> 300 nm) aggregates were

observed after solvent evaporation for the simple linear

diblockcopolymers (Figure 2A; see Figure S8 in the

Supporting Information). There was no evidence for well-

defined, self-assembled nanoparticles.

Initially, we produced simple linear AB amphiphilic

diblockcopolymers (see the Supporting Information), which

do not self-assemble to form organic nanoparticles, using

aqueous phase ATRP.^[21,22]Well-defined branched block-

[*] T. He, C. T. Yeoh, Prof. A. I. Cooper, Prof. S. P. Rannard

Department of Chemistry, University of Liverpool

Crown Street, Liverpool (UK)

Fax: (+44)15-1794-2304

E-mail: aicooper@liv.ac.uk

srannard@liv.ac.uk

D. J. Adams, M. F. Butler

Unilever Corporate Research

Colworth, Sharnbrook, Bedfordshire, MK44 1LQ (UK)

[**] The authors gratefully acknowledge Unilever Corporate Research

and EPSRC for funding (EP/C511794/1). S.R. acknowledges the

Royal Society for an Industrial Fellowship.

Our chemical synthesis strategy allows the rational design

and manipulation of nanoparticle size by varying the block

lengths. A systematic increase in average z-average particle

Supporting information for this article is available on the WWW

under http://www.angewandte.org or from the author.

Angew. Chem. Int. Ed. 2007, 46, 9243 –9247

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

9243

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In contrast to more

established polymerization

routes such as emulsion

polymerization, which pro-

duce spherical particles,

this method may be

extended to more complex

nanoscale

architectures.

For example, we synthe-

sized anisotropic dumbbell

structures with targeted

shapes at the multinano-

meter scale in a one-pot

reaction (Figure 3). The

one-pot living polymeri-

zation was carried out

exactly as before (40:60

OEGMA/nBuMA) except

for the addition of the

bifunctional initiator 5 in

the initial poly(OEGMA)

growth stage (Figure 3A).

This combined initiator

system (20:80 5/1) gener-

ates a mixture of linear

Figure 1. A) Synthesis of AB branched block copolymer by ATRP with introduction of the dimethacrylate

brancher 4. B) Schematic of branched copolymer structure in THF and collapse of the poly(nBuMA) branched

core in water. Diameters refer to z-average values determined by dynamic light scattering. bpy=2,2’-bipyridine.

poly(OEGMA)

chains

where the number-average

molecular weight of the

“bifunctional” polymer derived from

(roughly

80 OEGMA units) is approximately twice that of the polymer

derived from initiator 1 (roughly 40 units). Subsequent

addition of nBuMA and EGDMA produces a mixture of

branched AB and ABA blockcopolymers having poly-

(nBuMA) segments of identical length. The ABA copolymers

generated from initiator 5 have two propagating branching

chain ends, which are designed to form a statistically governed

number of bridging chains between the cores of the growing

spherical nanoparticles, hence forming dumbbell-like nano-

structures (Figure 3B).

The sample was dialyzed as before to form a stable

dispersion of polymer nanoparticles in water. TEM inves-

tigations (Figure 4; see Figure S12 in the Supporting

Information) revealed structures very different from those

observed for particles prepared in the absence of initiator 5.

Of the 900 particles measured by TEM, 56% were found to

have elongated, dumbbell-like morphologies resembling two

conjoined spheres. The degree of elongation and separation

between the conjoined spheres was found to vary (see

Figure 4D and Figure S15 in the Supporting Information as

well as the associated discussion). Structures of this type were

never observed for the branched AB blockcopolymer formed

using initiator 1 alone; equivalent TEM analysis showed

exclusively spherical structures (Figure 2D). Cryogenic TEM

analysis of a frozen aqueous solution of the mixed AB/ABA

branched copolymers also showed the presence of anisotropic

particles. The nanoparticles observed using cryogenic TEM

(see Figure S13 in the Supporting Information) were more

oblate and exhibited less structural definition, most likely

because of aqueous solvation of the poly(OEGMA) chains.

Figure 2. A) TEM image of film formed by deposition of a heteroge-

neous suspension of phase-separated linear poly(OEGMA)-b-poly-

(nBuMA) diblock copolymer in water. B) TEM image of branched block

copolymer nanoparticles deposited from a homogeneous aqueous

solution. C) DLS data for branched block copolymer nanoparticles in

water; z-average diameter=32.5 nm. D) Histogram showing particle

size distribution for these particles by TEM analysis (900 particles

measured; mean diameter=43.2 nm; standard deviation=10.6 nm).

diameter determined by DLS after dialysis was observed for a

series of three AB branched blockcopolymers (31.2 nm,

32.5 nm, 37.7 nm) with poly(OEGMA)/poly(nBuMA) block

ratios of 40:40, 40:60, and 40:80 repeat units, respectively.

9244 www.angewandte.org

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Angew. Chem. Int. Ed. 2007, 46, 9243 –9247

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Angewandte

Chemie

Figure 3. A) Targeted synthesis of dumbbell-like polymer nanoparticles by introduction of the difunctional ATRP initiator 5. B) Schematic

representation of a polymer dumbbell nanostructure showing two poly(OEGMA)-protected poly(nBuMA) cores covalently connected by a

difunctional poly(OEGMA) chain derived from initiator 5. It should be noted that the DLS diameter is a spherical average and that this is a poor

estimate for anisotropic structures.

These cryoscopic measurements in situ rule out complex

association phenomena that can occur during drying as a

mechanism for formation of the structures. While inherently

anisotropic polymer colloids have been prepared before,^[27]

we believe that this is the first example of a direct, targeted

synthesis of such materials.

There are two nonexclusive mechanisms by which the

dumbbells could be formed: coupling of preformed spheres or

a concerted growth process. The size distribution for the

spherical particles was found to be very similar to the size

distribution for the component halves of the dumbbells (see

Figure S15 in the Supporting Information), although these

statistics would be expected for both stepwise and concerted

processes. Preliminary TEM studies of the growth mechanism

suggest that some nascent dumbbell structures (< 20 nm in

length) are formed at quite low nBuMA conversions

(<30%). This implies that the process is, at least in part, a

concerted growth mechanism. These same studies also

suggest, however, that the proportion of dumbbell structures

increases with nBuMA conversion, making it likely that

particle–particle coupling plays a role at higher monomer

conversions. The importance of phase separation between the

poly(OEGMA) and poly(nBuMA) blocks in forming the

well-defined dumbbell shape is as yet unclear, although it

should be noted that less structural definition was apparent

for in situ cryo-TEM experiments (see Figure S13 in the

Supporting Information).

The schemes presented in Figure 1B and Figure 3B are

very simplistic. First, the structures are composed of many

more covalently linked chains. A spherical poly(OEGMA)₄₀-

b-(poly(nBuMA)-co-EGDMA)₆₀particle with a diameter of

32.5 nm would have a volume of 17974 nm³and a mass of

1.8 10^À17g, if one assumes a nominal bulkdensity of

1 gcm^À3. This would correspond to a covalently linked

assembly of more than 600 primary polymer chains and a

molar mass per particle of > 1 10⁷gmol^À1, assuming that the

Angew. Chem. Int. Ed. 2007, 46, 9243 –9247

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.angewandte.org

9245

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Communications

average 6 units per chain) is in low concentration relative to

nBuMA (on average 60 units per chain).

These data support unambiguously the formation of

unimolecular species rather than physical aggregates. The

control over particle structure is imperfect: 43% of spherical

species were observed in addition to the target dumbbells.

This compares favorably, however, with many self-assembled

blockcopolymer systems where the structure of interest may

often be a minority species. A very small number of higher-

order structures are also observed (< 1%), as would be

expected in a statistically governed reaction; both linear and

triangular structures consisting of three cores are evident in

the distribution (Figure 4A,B marked with arrows). The very

small percentage of higher-order structures suggests that

steric factors and internal loops (see above) may limit the

growth of these structures, which should, on average, have

sufficient bifunctional “arms” to bridge much more exten-

sively at a 20:80 ratio of 5/1. The statistical distribution of the

nanostructures can be changed by varying the ratio of the

mixed initiators, 1 and 5. Spherical nanostructures are formed

exclusively when initiator 1 is used while a 80:20 ratio of

initiators 1 and 5 gives mostly (56%) dumbbell nanostruc-

tures (Figure 4A,B). At a lower 5/1 ratio (10:90) just 16% of

dumbbell structures were observed (see Figure S14 in the

Supporting Information), the remainder being spherical

nanoparticles. By contrast, a 23:77 ratio of 5/1 produced

mainly higher-order unimolecular structures with three or

more linked cores (Figure 4C). Macroscopic formation of a

gel, as a result of extended networkformation, was observed

when the ratio of initiators 5 and 1 was increased to 25:75. The

strong sensitivity of the system to the concentration of the

difunctional linker 5 is characteristic of a combined step-

growth/chain-growth mechanism with substantial increase in

molecular weight at higher monomer conversions.^[14–17]

In summary, we have demonstrated the direct, targeted,

one-pot synthesis of spherical and anisotropic nanostructures

on a multigram scale from simple vinyl monomers. Although

the basic synthetic strategy is similar to that used to generate

star polymers,^[22–26]the size and topology of the resulting

spherical and dumbbell nanostructures are unprecedented for

a one-pot synthesis. These reproducible and simple synthetic

techniques offer researchers a design protocol for complex

functional nanostructures with specific placement of func-

tionality. More elaborate nanostructures are readily envis-

aged, for example, by using a derivatized metal or inorganic

nanoparticle or biomolecule as a component of the initiating

system. Strategies of this type are enabled by the relative ease

with which a wide range of molecules and nanostructures

have been functionalized with ATRP initiators. The core-shell

morphology of these particles suggests applications in encap-

sulation and controlled release. Anisotropic particles may be

useful, for example, as carriers in biological systems where

size, chemical functionality, and shape are all important. Our

route also presents a number of challenges, for example, in

developing strategies to achieve control over the breadth of

structures arising from the statistical nature of the branching

process. A key challenge will be to develop improved routes

with enhanced structural control without sacrificing the

simplicity, versatility, and scalability of the approach.

Figure 4. A,B) High- and low-magnification TEM images of dumbbell-

like polymer nanoparticles (56% by number) and spherical particles

(43%) produced using 20:80 ratio of 5/1. A very small number of

higher-order structures (0.5% with three cores, 0.05% with four) were

also observed (marked with arrows). C) Inset (same scale as (B))

showing higher-order structures at a ratio of 23:73 5/1. D) Expansions

showing five dumbbell structures formed using 20:80 ratio of 5/1 and

illustrating the range of topologies in the sample.

molar mass per primary chain is 17000 gmol^À1. Given the

nature of the DLS measurement, this simple “hard-sphere”

comparison and bulkdensity estimate are crude approxima-

tions; nonetheless, it is clear that these particles have very

high molar masses and this explains the failed attempts at

size-exclusion chromatography (see Supporting Information).

A second simplification is that the ABA branched block

copolymers derived from 5 may not always grow between two

distinct hydrophobic monomer cores, as shown in Figure 3B

but might be incorporated into just one core as “loops” or

pendant chains. Similarly, multiple ABA chains may link

poly(nBuMA) core masses. It is also conceivable that the

poly(nBuMA) cores themselves may spread and bridge,

rather than exclusive linking through poly(OEGMA) chains

(Figure 3B). However, preliminary experiments show that

perfectly cleavable dumbbells may also be synthesized—for

example, by building disulfide links into the difunctional

initiator, 5—which supports a model where the dumbbells are

exclusively linked through these ABA chains. Moreover,

there is a total absence of dumbbell structures in the AB

branched blockcopolymer. A further simplification is the

representation of clean blocking. Since the nBuMA monomer

is added at around 85% OEGMA conversion, it is likely that

a statistically gradient exists between the poly(OEGMA) and

poly(nBuMA) blocks, although the unreacted OEGMA (on

9246 www.angewandte.org

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Angew. Chem. Int. Ed. 2007, 46, 9243 –9247

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[8] D. J. Pochan, Z. Y. Chen, H. G. Cui, K. Hales, K. Qi, K. L.

Experimental Section

Wooley, Science 2004 , 306 , 94 – 97.

Full details of the synthetic procedures used to prepared the polymers

are included in the Supporting Information. A typical synthetic

procedure (for the linear diblockcopolymer, poly(OEGMA) ₄₀-b-

poly(nBuMA)₆₀was as follows: OEGMA (2.04 g, 6.8 mmol), CuBr

(24.5 mg, 0.17 mmol), bpy (53.1 mg, 0.34 mmol), and solvent (iso-

propanol/water (92.5:7.5 v/v; 4.2 mL) were added to a Schlenkflask

(50 mL). The reaction mixture was bubbled with nitrogen for 40 min

to completely remove the oxygen, before EBriB (ethyl 2-bromoiso-

butyrate) (25.0 mL, 33.2 mg, 0.17 mmol) was added with a micro-

syringe. The polymerization was carried out at ambient temperature

(ꢀ208C) under N₂. In another 50-mL Schlenkflask, CuCl (16.9 mg,

0.17 mmol), byp (53.1 mg, 0.34 mmol), nBuMA (1.45 g, 10.2 mmol)

and 5.8 mL of the water–alcohol solvent mixture were added, and this

mixture was bubbled with N₂for 1 h. After the conversion of

OEGMA reached around 85%, the mixture from the second flask

was added into the first flaskrapidly using a syringe. The block

copolymerization reaction was carried at ambient temperature, and

samples were taken periodically from the reaction mixture for

¹H NMR analysis. After the consumption of the nBuMA monomer

had reached around 90%, the polymerization was stopped by adding

THF into the reaction mixture and exposing the sample to air.

[9] C. J. Hawker, K. L. Wooley, Science 2005 , 309 , 1200 – 1205.

[10] S. I. Stupp, V. LeBonheur, K. Walker, L. S. Li, K. E. Huggins, M.

Keser, A. Amstutz, Science 1997 , 276 , 384 – 389.

[11] J. S. Wang, K. Matyjaszewski, J. Am. Chem. Soc. 1995 , 117 ,

5614 – 5615.

[12] D. Benoit, V. Chaplinski, R. Braslau, C. J. Hawker, J. Am. Chem.

Soc. 1999 , 121 , 3904 – 3920.

[13] J. Chiefari, Y. K. Chong, F. Ercole, J. Krstina, J. Jeffery, T. P. T.

Le, R. T. A. Mayadunne, G. F. Meijs, C. L. Moad, G. Moad, E.

Rizzardo, S. H. Thang, Macromolecules 1998 , 31 , 5559 – 5562.

[14] S. Graham, P. A. G. Cormack, D. C. Sherrington, Macromole-

cules 2005 , 38 , 86 – 90.

[15] F. Isaure, P. A. G. Cormack, D. C. Sherrington, Macromolecules

2004 , 37 , 2096 – 2105.

[16] N. OꢀBrien, A. McKee, D. C. Sherrington, A. T. Slark, A.

Titterton, Polymer 2000 , 41 , 6027 – 6031.

[17] F. Isaure, P. A. G. Cormack, S. Graham, D. C. Sherrington, S. P.

Armes, V. Bütün, Chem. Commun. 2004 , 1138 – 1139.

[18] B. L. Liu, A. Kazlauciunas, J. T. Guthrie, S. Perrier, Macro-

molecules 2005 , 38 , 2131 – 2136.

[19] V. Butun, I. Bannister, N. C. Billingham, D. C. Sherrington, S. P.

Armes, Macromolecules 2005 , 38 , 4977 – 4982.

[20] I. Bannister, N. C. Billingham, S. P. Armes, S. P. Rannard, P.

Findlay, Macromolecules 2006 , 39 , 7483 – 7492.

[21] X. S. Wang, S. P. Armes, Macromolecules 2000 , 33 , 6640 – 6647.

[22] S. McDonald, S. P. Rannard, Macromolecules 2001 , 34 , 8600 –

8602.

Received: July 25, 2007

Published online: November 15, 2007

Keywords: atom-transfer polymerization · nanoparticles ·

polymerization

[23] J. Xia, X. Zhuang, K. Matyjaszewski, Macromolecules 1999 , 32 ,

4482 – 4484.

[1] P. W. K. Rothemund, Nature 2006 , 440 , 297 – 302.

[2] K. B. Thurmond, T. Kowalewski, K. L. Wooley, J. Am. Chem.

Soc. 1996 , 118 , 7239 – 7240.

[3] R. K. OꢀReilly, C. J. Hawker, K. L. Wooley, Chem. Soc. Rev.

2006 , 35 , 1068 – 1083.

[4] W. Schärtl, Adv. Mater. 2000 , 12 , 1899 – 1908.

[5] S. Y. Liu, J. V. M. Weaver, Y. Q. Tang, N. C. Billingham, S. P.

Armes, K. Tribe, Macromolecules 2002 , 35 , 6121 – 6131.

[6] S. Y. Liu, S. P. Armes, J. Am. Chem. Soc. 2001 , 123 , 9910 – 9911.

[7] V. Butun, N. C. Billingham, S. P. Armes, J. Am. Chem. Soc. 1998 ,

120 , 12135 – 12136.

[24] K.-Y. Baek, M. Kamigaito, M. Sawamoto, Macromolecules 2001 ,

34 , 215 – 221.

[25] X. Zhang, J. Xia, K. Matyjaszewski, Macromolecules 2000 , 33 ,

2340 – 2345.

[26] H. Gao, K. Matyjaszewski, Macromolecules 2006 , 39 , 3154 –

3160.

[27] Z. Q. Yang, W. T. S. Huck, S. M. Clarke, A. R. Tajbakhsh, E. M.

Terentjev, Nat. Mater. 2005 , 4 , 486 – 490.

Angew. Chem. Int. Ed. 2007, 46, 9243 –9247

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Article Doi

Direct synthesis of anisotropic polymer nanoparticles

DOI: 10.1002/anie.200703348

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Article abstract of DOI:10.1002/anie.200703348

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