Authors:S. Papp, L. Kőrösi, B. Gool, T. Dederichs, P. Mela, M. Möller, and I. Dékány
Gold nanoparticles (Au NPs) were prepared by the reduction of HAuCl4 acid incorporated into the polar core of poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer micelles dissolved in toluene. The formation of Au NPs was controlled using three reducing agents with different
strengths: hydrazine (HA), triethylsilane (TES), and potassium triethylborohydride (PTB). The formation of Au NPs was followed
by transmission electron microscopy, UV–Vis spectroscopy, isothermal titration calorimetry (ITC), and dynamic light scattering
(DLS). It was found that the strength of the reducing agent determined both the size and the rate of formation of the Au NPs.
The average diameters of the Au NPs prepared by reduction with HA, TES, and PTB were 1.7, 2.6, and 8 nm, respectively. The
reduction of Au(III) was rapid with HA and PTB. TES proved to be a mild reducing agent for the synthesis of Au NPs. DLS measurements
demonstrated swelling of the PS-b-P2VP micelles due to the incorporation of HAuCl4 and the reducing agents. The original micellar structure rearranged during the reduction with PTB. ITC measurements revealed
that some chemical reactions besides Au NPs formation also occurred in the course of the reduction process. The enthalpy of
formation of Au NPs in PS-b-P2VP micelles reduced by HA was determined.
Authors:A. Tercjak, M. Larrañaga, M. Martin, and I. Mondragon
The main aim of this research was the generation
of new intelligent materials, in this case thermoreversible material, based
on epoxy matrix modified with semi-crystalline block copolymers. In this study,
the epoxy system based on a diglycidyl ether of bisphenol-A (DGEBA), was cured
with a stoichiometric amount of an aromatic amine hardener, 4,4’-methylene
bis (3-chloro-2,6-diethylaniline) (MCDEA). A diblock copolymer of polyethylene-b-poly(ethylene
oxide) (PEOE) was used as self-assembly agent.
of the samples modified by addition of PEOE were studied by using transmission
optical microscope (TOM) equipped with a hot stage. Additionally, morphology
generated in the sample was studied by atomic force microscopy (AFM).
Authors:J. Haigh, C. Nguyen, R. Alamo, and L. Mandelkern
The crystallization and melting of three model polyethylenes of different chain structures have been studied. The polymers studied were a linear copolymer, hydrogenated poly(butadiene); a hydrogenated poly(butadiene)-atactic poly(propylene) diblock copolymer; and a three-arm star hydrogenated poly(butadiene). An important feature of this work was that the crystallizing portions of the copolymers all have the same molecular lengths.It was found that the overall crystallization rate decreases steadily from a linear to a diblock to the star copolymer. The differences in crystallization rates are related primarily to the activation energy for segmental transport. The non-crystallizable structure affects the segmental mobility to different degrees. An estimation of this effect is presented from the analysis of the overall crystallization rates using classical nucleation theory. In spite of thedifferences in their molecular structure, there are no major differences in the supermolecular structure of samples crystallized rapidly or slowly cooled.The melting process followed by DSC of the isothermally crystallized linear and star copolymers shows two endothermic peaks at intermediate undercoolings. The double melting is associated with a partitioning of crystallizable ethylene sequences during crystallization. The longest sequences are preferentially selected in the early stages of the crystallization. Single melting peaks are obtained for high and very low undercoolings for the linear and the star copolymers as well as for the diblock in the whole range of temperatures. The lack of the second, lower melting endotherm in the diblock could be associated with the influence in the crystallization process of the amorphous block in the microphase segregated melt.
Representative synthesis route of triblock copolymer
The resulting diblockcopolymer (P t BMA- b -PGMA-SSZ) was used as a polymeric chain transfer agent to initiate polymerization of styrene, to get the third block of
Authors:Halina Kaczmarek, Marta Chylińska, and Marta Ziegler-Borowska
Other example of PS modification is the synthesis with oligofluorene pendants via Friedel–Crafts reaction, leading to non-conjugated fluorescent polymer for photoelectric devices [ 9 ] or manufacturing the stereoregular diblockcopolymer of PS and
, M. Poliakoff European Journal of Organic Chemistry 2015 , 2015 , 6141 – 6145
“ Influence of microphase morphology and long-range ordering on foaming behavior of PE-b-PEO diblockcopolymers ” Y. Xu , T. Liu , W.-k. Yuan
Authors:C. G. Mothé, A. D. Azevedo, W. S. Drumond, S. H. Wang, and R. D. Sinisterra
( Fig. 1 a) or smooth surface ( Fig. 1 c). Similar results have been reported by others authors for PLA-PEG [ 5 , 13 , 17 – 21 ] diblockcopolymers. The roughness of the surface ( Fig. 1 a) could be attributed to the presence of hydrophobic (PLLA) and