Intrinsic viscosity block copolymers

Intrinsic viscosity measurements on polymers isolated after the chain-effect reactions showed that the materials were true block copolymers, their viscosities being identical with those of copolymers prepared by... 

Keywords. Dendrimers, Hyperbranched macromolecules. Block copolymers. Surface functionalization, Solvatochromism, Intrinsic viscosity... 

Initial intrinsic viscosity, dl/g Free polyfmethyl acrylate) Free polystyrene Block copolymer... 

The GPC analysis of block copolymers is handicapped by the difficulty in obtaining a calibration curve. A method has recently been suggested to circumvent this difficulty by using the calibration curves of homopolymers. This method has been extended so that the calibration curves of block copolymers of various compositions can be constructed from the calibration curve of one-component homopolymers and Mark-Houwink parameters. The intrinsic viscosity data on styrene-butadiene and styrene-methyl methacrylate block polymers were used for verification. The average molecular weight determined by this method is in excellent agreement with osmometry data while the molecular weight distribution is considerably narrower than what is implied by the polydispersity index calculated from the GPC curve in the customary manner. 

The intrinsic viscosity data on styrene (S)-butadiene (B) block copolymer measured by Utracki and co-workers (4) are replotted in... 

Viscometry has been used extensively to provide information on the hydrodynamic properties of solutions of block copolymer micelles. The specific viscosity, J7sP, divided by the concentration, can be used to determine the intrinsic viscosity, [r/], by extrapolation via... 

Here kH is the Huggins coefficient. The intrinsic viscosity decreases and the Huggins coefficient increases, as micelles become smaller. On micellization, ijsp/c has been observed to increase for some systems but to decrease for others, and unfortunately there are no firm rules governing which case will prevail for a given block copolymer solution. The viscosities of polymer solutions are measured in capillary flow viscometers, which are described in detail by Macosko (1994). 

Research grade poly(styrene-b-butadiene-b-styrene), designated as TR-41-1647, TR-41-1648, and TR-41-1649, were received from Shell Development Co. These block copolymers contain 26.8, 29.3, and 48.2 wt% polystyrene (PS), respectively. The average molecular weights, determined by intrinsic viscosity measurements in toluene at 30°C, were found to be 7-36-6, 16-78-16, and 14-30-14 in units of thousands. The microstructure of polybutadiene (PB) blocks was found to contain about 40 mol% in cis-1,4, 50% in trans-1,4, and 10% in 1,2 units. 

The oligomer molecular weights were characterized by both UV-visible spectra (20, 21) and/or potentiometric titrations (22, 23). Details of the measurements are provided in these papers. The block copolymers also were characterized by intrinsic viscosity and in some cases by membrane osmometry and gel permeation chromatography. Additional characterization studies are continuing and will be reported later. A typical synthesis of a 5000-5000 polysulfone-S-polycarbonate-A copolymer via interfaciar polymerization is described below. 

The architecture of a copolymer (random, block, graft) has also to be taken into account, as Revillon [34] has shown by SEC with RI, UV, and viscosity detection. Intrinsic viscosity varies largely with molar mass according to the type of polymer, its composition, and the nature of its components. Tung [35] found that for block copolymers in good SEC solvents the simpler first approach (Eq. 4) is more precise. 

A model series consisting of six ethylene-propylene block copolymers (PP/EPR) has been investigated. While the flowability of their matrix (MFR 45 dgmin x), the rubber content (about 23 wt %) and the amount of C2 in the E/P rubber have been fixed, their intrinsic viscosity (IV) has been varied systematically from 1.7 to 6 dg 1 1 (which corresponds roughly to Mw from 150 to 1000 kg mol x). A detailed description of the non-nucleated materials and their performance has been published elsewhere [168]. 

Figure 4.1. Intrinsic viscosity as a function of temperature for poly(iso-prene- 7-styrene) block copolymers I.S. 6, I.S. 7, and I.S. 8 dissolved in cyclohexane. (Girolamo and Urwin, 1971.)...

Figure 12.1.6 shows two different behaviors for unassociated and associated block copolymers. The first type has a linear relationship between viscosity and concentration whereas with the second there is a rapid increase in viscosity as concentration increases. This is the best described as a power law function. Two polymers in combination have different reactions when dissolved in different solvents (Figure 12.1.7). In MEK, intrinsic viscosity increases as polymer concentration increases. In toluene, intrinsic viscosity decreases as polymer concentration increases. The polymer-solvent interaction term for MEK is very small (0.13) indicating a stable compatible system. The interaction term for toluene is much larger (0.58) which indicates a decreased compatibility of polymers in toluene andlowers viscosity of the mixture. Figure 12.1.8 explicitly shows that the behavior of...

Application of Mark-Houwink constants. It is well known that the plot of log ri2M V. Fr, the so-called universal calibration , is obeyed by structurally different polymers including random, block and graft copolymers. Therefore, the use of [rj M should be a theoretically reliable procedure for calibration. PS, PMMA, and their random and block copolymers having the same molecular massj)ut different Fr had different intrinsic viscosities [1]. The plot of log([f/]M ) v. Fr for these polymers and copolymers fitted satisfactorily on the universal calibration curve which was established using a series of PS samples of various molecular masses. 

This method was applied to styrene-isoprene block copolymers of AB and ABA types having relatively narrow molecular mass distributions [11]. Universal calibration curves for PS, polyisoprenes, and their block copolymers fell on the same line. Conversion to log M v. Fr was accomplished by obtaining intrinsic viscosities of these copolymers, which were closely related to those of the corresponding homopolymers of equal molecular mass by... 

Continuous measurement of viscosity. The accuracy of the Mark-Houwink equation will be improved if the intrinsic viscosity of a fraction at each retention volume can be measured continuously. An automatic viscometer having a capillary of 0.5 mm in diameter and a length of 200 mm was constructed and applied to the estimation of molecular mass of di- and triblock copolymers of polystyrene-polyisoprene P(S-IP) and di-block copolymer of P(S-MMA) [32]. In the case of copolymers which have homogeneous... 

The intrinsic viscosities of the graft copolymers were in the range of 1.3 1.9 dl/g, compared to O.S- l.l dl/g for their polyimide precursors. The block copolymers exhibited intrinsic viscosities of 2.2 4.6 dl/g, compared to 1.0-1.4 dl/g for the end-capped polyimides. The increase in the viscosity of the graft and block copolymers was the lowest when the most rigid polyimides were used. 

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