Ming Jiang

Intermacromolecular complexes due to specific interactions. 12. Graft-like hydrogen bonding complexes based on pyridyl-containing polymers and end-functionalized polystyrene oligomers

Soluble graft-like complexes were obtained via hydrogen bonding interaction between poly(4-vinyl pyridine) (PVPy) or poly(butyl acrylate-co-4-vinyl pyridine) (BVPy) and mono-carboxy terminated polystyrene (MCPS). The hydrogen-bonding interaction was evidenced by 13 C NMR and FT-IR. In the blend solution, the grafting of MCPS onto PVPy or BVPy backbones led to graft-like complexes showing much larger average hydrodynamic radius kRhl than is shown by either component alone, the conformation of PVPy backbone undergo chain extension due to the steric repulsion of grafted MCPS chains. Moreover, both viscometry and LLS showed a strong effect of molar mass of MCPS on grafting, e.g. the number of branches on each PVPy backbone decreased from 330 to 3 as the molar mass increased from 1.8k to 23.4k. Fluorescence measurements in the blend solutions supported these conclusions. The DSC results of PVPy/MCPS blends in bulk showed two-phase structures as the hydrogen bonding interaction existing between carboxyl end and PVPy is not enough to cause complete mixing. Besides, the thermal history greatly influenced the phase behavior of the blends as the hydrogen bonding is sensitive to temperature. For the blends containing MCPS and BVPy-34 with lower VPy content and much lowerTg, miscibility over the whole composition range was obtained. q 2000 Elsevier Science Ltd. All rights reserved.

Intermacromolecular complexes due to specific interactions. 13. Formation of micelle-like structure from hydrogen-bonding graft-like complexes in selective solvents

The complexation between poly(4-vinyl pyridine) (PVPy) and mono-carboxy terminated polystyrene (MCPS) in chloroform leads to the formation of a graft-like supramolecular architecture. LLS and fluorescence spectroscopy have been used to monitor the self-assembly process of the “graft” copolymers in a selective mixed solvent of chloroform/toluene which is a solvent for MCPS but a nonsolvent for PVPy. Adding toluene to PVPy/MCPS-1.8 blend solution in chloroform leads to a stable and clear solution indicating the formation of the micellelike core-shell structure with the core and shell made of PVPy and MCPS, respectively. Here, the cores and shells are linked by hydrogen bonding. The final micelle-like particles are narrowly distributed and very stable on standing. Adding the blend solution of PVPy and MCPS in chloroform to an excess of toluene also produces micelles but these have a much smaller average hydrodynamic radius (kRhl) than those prepared by adding toluene to the blend solution. As the molar mass of MCPS is increased, the size of micelle-like structures increases dramatically. q 2000 Elsevier Science Ltd. All rights reserved.

Preparation and association behavior of diblock copolymer ionomers based on poly(styrene-b-ethylene-co-propylene)

Two kinds of diblock ionomer were prepared by carboxylating and sulfonating the polystyrene (PS) block of a commercial product of poly (styrene-block-ethylene-co-propylene) (SEP). The PS block was partially carboxylated via a mild Friedel‐Crafts acetylation and a subsequent haloform oxidation. The carboxylation only slightly changed the molecular weight distribution of the SEP at low carboxylation levels typical for ionomers. Acetyl sulfate was used as the sulfonating agent for sulfonation. Both carboxylated SEP and sulfonated SEP ionomers with either lithium or zinc as counterions exhibit increased decomposition temperature and higher Tg of the PS blocks compared with their base resin as a result of intermolecular association due to the interactions of ionic groups. The ionomers show apparently increased viscosity than SEP. The data indicate that the sulfonate groups have stronger ability of association than the corresponding carboxylate groups, while zinc ions stronger than lithium ions. A combination of static and dynamic light scattering directly provides semi-quantitative information of association of the diblock ionomers, e.g., for the ionomers with functionality of 5.3 mol%, the association number was found to range from 8 to 17 depending on the nature of the cationic and anionic groups incorporated. # 1999 Elsevier Science Ltd. All rights reserved.

Micelle-like particles formed by carboxylic acid-terminated polystyrene and poly(4-vinyl pyridine) in chloroform/methanol mixed solution

Abstract Preparation and characterization of isolated particles and clusters of carboxylic acid-terminated polystyrene (CPS) and poly(4-vinyl pyridine) (P4VP) blends in chloroform/methanol (9/1, v/v) solution are reported. In chloroform CPS–P4VP blends form graft-like structure due to the interaction between terminal carboxylic acid and 4VP units. Upon addition of methanol, isolated particles and clusters with micelle-like structure were prepared. Dynamic light scattering (DLS) results and transmission electron microscopy (TEM) images both suggest the existence of isolated particles and clusters with micelle-like structure in the mixed solution. The effects of weight ratio of CPS to P4VP and addition of copper ion on the size of isolated particles and clusters were also investigated.

A novel fluorescence probe for micellization of amphiphilic molecules in water based on intramolecular exciplex formation

A novel friction-sensitive fluoresence probe based on intramolecular exciplex formation, (9-anthrylmethyloxymethyl)pyrene (AMOP), was used to study the micellization of amphiphilic molecules such as sodium dodecyl sulfate (SDS) and hydrocarbon-modified polyethylene glyco (HM-PEG) in water. Results demonstrate that AMOP can serve as a sensitive probe for micellization of both SDS and HM-PEG. In addition, AMOP reveals information about the microviscosity of SDS and HM-PEG micelles, wich is in good agreement with the results obtained from other fluorescence probes based on intramolecular excimer such as dipyrenylpropane (Py(CH 2 ) 3 Py) and bis(1-pyrenylmethyl) ether (dipyme, PyCH 2 OCH 2 Py).