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Copolymer molar mass

Universal calibration measurement of Mark-Houwink coefficients for copolymers with homogeneous and known composition will give copolymer molar masses. [Pg.225]

SEC with light-scattering detection direct copolymer molar mass measurement for chemically homogeneous and segmented copolymers independent of their structure. [Pg.225]

Conventional GPC data processing is unable to determine other important polymer properties such as copolymer composition or copolymer molar mass. The reason is that the GPC separation is based on hydro-dynamic volume rather than the molar mass of the polymer and that molar mass calibration data are only valid for polymers of identical molecular structures. [Pg.441]

The major difficulty in the determination of the copolymer molar mass distribution is the fact that the GPC separation is based on the molecular size of the copolymer chain. Its hydrodynamic radius, however, is dependent on the type of the comonomers incorporated into the macromolecule as well as their placement (sequence distribution). [Pg.442]

In such cases, the copolymer molar mass M can be determined from the interpolation of homopolymer calibration curves M V) and the weight fractions w. of the comonomers k according to [1]... [Pg.442]

The calculation of copolymer molar mass averages and so on, and copolymer polydispersity D is done as in conventional GPC calculations using the copolymer molar mass calculated from Eq. (3). [Pg.442]

In cases where the number of heterocontacts can no longer be neglected, this simplifled reasoning breaks down and copolymer molar masses cannot be measured accurately by GPC alone. This is the case with statistical copolymers, polymers with only short comonomer sequences and high side-chain densities [2]. In such cases, more powerful and universal methods have to be employed (e.g., 2D separations) (see below). [Pg.442]

FOR Foroutan, M. and Khomami, M.H., Influence of copolymer molar mass on the thermodynamic properties of aqueous solution of an amphiphiUc copolymer, J. [Pg.110]

The number average of the molar masses of the homosequences A or B and the number average of the copolymer molar mass are... [Pg.299]

Pasch et al. have compared of copolymer molar masses from SEC and from LCCC for block copolymers PDMA-PMMA [61] and PS-PMMA [80]. From the molar mass of the individual blocks, which were measured under LCCC, the total molar masses of the block copolymers were calculated. Moreover, the expected nominal chemical composition was compared with the chemical composition determined by LCCC. While the molar mass of copolymers from SEC was used for comparison in some studies [61,80], molar mass of PS precursor used for preparation of corresponding copolymers has also been selected as reference value in [47]. Very good agreement of values was found, as documented by data in Table 6A,B extracted from [47,80]. [Pg.125]

Norbornene molar fraction in copolymer ( C NMR, 1,2,4-trichlorobenzene, 100 °C). Copolymer molar mass determined by viscosimetry in 1,2,4-trichlorobenzene at 135 °C. [Pg.431]

Copolymer molar mass determinations were made by size occlusion dnomatogn hy (SEC) using viscometric detection and universal calibration and are absolute. Glass transition temperatures were determined by diffowitial scanning calorimetiy (DSC) undo nitrogo) at a heating rate of 10 °C/min. [Pg.140]

Several attempts have been made to solve the calibration dilemma. Some are based on the tmiversal calibration concept, which has been extended for copolymers another approach to copolymer calibration is multiple detection. The advantages of multiple detection lie in its flexibility and the fact that it yields the composition distribution as well as molar masses for the copolymer under investigation [7]. This method requires molar mass calibration and an additional detector response calibration to determine the chemical composition at each point of the elution profile. No other kind of information, parameters or special equipment are necessary to carry out this kind of analysis and to calculate compositional drift, bulk composition, and copolymer molar mass [7a],... [Pg.372]

The major difficulty in the determination of the copolymer molar mass distribution is the fact that the GPC separation is based on the molecular size of the copolymer chain. Its hydrodynamic radius, however, is dependent on the type of comonomers incorporated into the macromolecule and their placement (sequence distribution). Consequently, there can be a coelution of species having different chain lengths and different chemical compositions. The influence on the chain size of different comonomers copolymerized into the macromolecule can be measured by GPC elution of homopolymer standards of this comonomer. Unfortunately, the influence of the comonomer sequence distribution on the hydrodynamic radius cannot be described explicitly by any theory at present However, there are limiting cases that can be discussed to evaluate the influence of the comonomer placement in a macromolecular chain. [Pg.373]

Copolymer molar mass averages etc. and copolymer polydispersity... [Pg.374]

Copolymer characterization copolymer composition distribution, copolymer molar mass... [Pg.183]

An independent task of copolymer analysis is the determination of meaningful copolymer molar masses. Obviously, results based on a single molar mass calibration generated with standards will not give accurate results, as the calibration will depend on the local composition of the species. A way to overcome this calibration dilemma is the use of online viscometers. An empirical method for samples with few hetero-contacts (e.g., block copolymers and graft copolymers) is using the multiple concentration detector approach. [Pg.190]

From a SEC point of view, an AB block copolymer, where a sequence of comonomer A is followed by a block of B units, is a simple copolymer. The only hetero-contact in this chain is the A-B link, the A and B segments of the block copolymer will hydrodynamicaUy behave like a pure homopolymer of the same chain length. In the case of long A and B segments, the A-B link acts as a defect position and will not change the overall hydrodynamic behavior. Consequently, the molar mass of the copolymer chain can be approximated by the molar masses of the respective segments. Similar considerations are true for ABA, ABC, and other types of block stmctnres and for comb-shaped copolymers with low side-chain densities. In snch cases, the copolymer molar mass can be determined from the interpolation of the two homopolymer calibration curves M V) and the weight fractions of the comonomers k [26] ... [Pg.190]

The calculation of copolymer molar mass averages and copolymer polydispersity is made as in conventional SEC... [Pg.190]

Volume fractions imply a temperature dependence and, as they are defined in equation (38), neglect excess volumes of mixing and, very often, the densities of the copolymer in the slate of the solution are not known correctly. However, volume fractions can he calculated without the exact knowledge of the copolymer molar mass (or its averages). Base mole fractions are seldom applied for copolymer systems. The value for A o, the molar mass of a basic unit of the copolymer, has to he determined according to the corresponding average chemical composition. Sometimes it is chosen arbitrarily, however, and has to he specified. [Pg.32]


See other pages where Copolymer molar mass is mentioned: [Pg.441]    [Pg.442]    [Pg.6]    [Pg.300]    [Pg.208]    [Pg.52]    [Pg.428]    [Pg.434]    [Pg.59]    [Pg.369]    [Pg.370]    [Pg.135]    [Pg.372]    [Pg.374]    [Pg.190]    [Pg.239]    [Pg.10]    [Pg.334]   


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