Using Polystyrene-block-poly(acrylic acid)-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

Summary

We report protocols for “polymerizing” various types of polymer-encapsulated metal nanoparticles into long chains of “homo-“ and “co-polymers”.

Abstract

We present a template-free method for “polymerizing” nanoparticles into long chains without side branches. A variety of nanoparticles are encapsulated in polystyrene-block-poly(acrylic acid) (PSPAA) shells and then used as monomers for their self-assembly. Spherical PSPAA micelles upon acid treatment are known to assemble into cylindrical micelles. Exploiting this tendency, the core-shell nanoparticles are induced to aggregate, coalesce, and then transform into long chains. When more than one type of nanoparticles are used, random and block “copolymers” of nanoparticles can be obtained. Detailed procedures are reported for the PSPAA encapsulation of nanoparticles, homo- and co-polymerization of the core-shell nanoparticles, separation and purification of the resulting nanoparticle chains. Transformations of single-line chains into double- and triple-line chains are also presented. The synergy between the polymer shell and the embedded nanoparticles leads to an unusual chain-growth polymerization mode, giving long nanoparticle chains that are distinct from the products of the traditional step-growth aggregation process.

Introduction

Despite great advances in the synthesis of nanoparticles over the past two decades, their orderly assembly remains a great challenge. Our synthetic capabilities in putting the basic building blocks together are of critical importance for the exploration and exploitation of their synergistic effects and collective properties. Thus, developing new reaction pathways and exploring the underlying mechanisms are the stepping stones towards the rational synthesis of complex nanodevices.

Among the rich structural variety of possible nanoparticle assemblies, one-dimensional (1D) chains have shown useful applications in nanoelectronics, optoelectron....

Protocol

Caution: Please consult all relevant material safety data sheets (MSDS). Some chemicals used in these syntheses are corrosive, toxic and possibly carcinogenic. Nanomaterials may have unrecognized hazards as compared to their bulk counterparts. Please use appropriate safety practices when performing reaction, including the use of fume hood and personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes, etc.).

1. Synthesis of Metal Nanoparticles

Note: All glassware used in the syntheses are washed with aqua regia (CAUTION: highly acidic and corrosive, handle with caution and dis....

Results

The nanoparticle monomers and chains are characterized by TEM. Figure 1 shows the representative TEM images of the PSPAA encapsulated monomers, confirming the morphologies and sizes (Figure 1). As some monomers typically remain in the sample after the “polymerization”, the sample is usually purified and concentrated before being used for TEM characterization. A stain was introduced during the preparation of the TEM samples by mixing the sample solution with 1% ammonium molybdate, in orde.......

Discussion

The mechanistic details of the syntheses are reported and discussed in the previous publications.^20,21 Here we focus on the rationales of the synthetic conditions. For the polymerization of nanoparticles, it is preferred that nanoparticles of uniform size are used. We follow literature procedures to obtain the uniform Au nanoparticles,²³ Au nanorods,²⁴ and Te nanowires.²⁵ In general, better size uniformity can be obtained when the nucleation and growth stages are separated.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Gold(III) chloride trihydrate, ACS reagent, ≥49.0% Au basis	Sigma-Aldrich	G4022	HAuCl4
Sodium citrate dihydrate, 99%	Alfa Aesar	A12274
Sodium borohydride, ≥99%	Sigma-Aldrich	71321, Fluka
Hexadecyltrimethylammonium bromide, ≥98%	Sigma-Aldrich	H5882	CTAB
Silver Nitrate, 99.9999% trace metals basis	Sigma-Aldrich	204390
L-ascorbic acid, BioXtra, ≥99.0%, crystalline	Sigma-Aldrich	A5960
Tellurium dioxide, ≥99%	Sigma-Aldrich	243450
Hydrazine monohydrate, 64-65%, reagent grade, 98%	Sigma-Aldrich	207942
Poly(styrene-b-acrylic acid) (PS154-PAA49)	Polymer Source	P4673A-SAA	PS16000-PAA3500
Poly(styrene-b-acrylic acid) (PS144-PAA28)	Polymer Source	P4002-SAA	PS15000-PAA1600
2-Naphthalenethiol, ≥99.0% (GC)	Sigma-Aldrich	88910, Fluka
Sodium dodecyl sulfate, 99%	Alfa Aesar	A11183
single wall carbon nanotubes, 99% ultra-pure	NanoIntegris	PC10344a
Sodium hydroxide	Sinopharm	S1900136
1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (sodium salt)	Avanti polar lipids	870160P	PSH
N,N-dimethylformamide	Merck	SA4s640012
Ethanol, absolute	Fischer	E/0650DF/17
Hydrochloric acid, 37%	Honey well	10189005	Dilute to 1 M before use