Copolymer, composition molar mass

Two general methods have been developed for the determination of copolymer composition and sequence, namely a method which uses a combination of mass spectral intensities and the chain statistics approach. " In the approach based on a combination of MS intensities one computes the average copolymer composition (molar fraction of A units in the copolymer), Ca-... 

The most recent development in separation is the development of high temperature interaction chromatography, which extends the composition distribution analysis to polyolefin copolymers of very low crystallinity, which is not possible to analyze by crystallization techniques. The analysis of complex polymers with different composition can be analyzed in a short time by solvent gradient interaction chromatography, SGIC, on an atomically flat surface like carbon or molybdenum sulfide packing. The addition of a second separation step by GPC (SGIC2D) provides the capability to obtain full composition-molar mass dependence. 

The behavior of ternary polymer mixtures containing a diblock copolymer with homopolymer and toluene as a function of mixture composition and temperature were investigated to obtain experimental phase diagram for solvent/copolymer/ homopolymer mixture. In order to avoid the complications associated with the microphase separation of block copolymers, the molar mass of block copolymer was kept low in our experiment (Madbouly Wolf, 2002). 

FIGURE 13.4 Using data from Figure 13.3, the fractional conversion of Am and VB are shown. A two-phase reaction occurs in which copolymer of Am and VB is produced up until 5500 s, after which homopolymers of Am form. Hence, a blend of copolyelectrolyte and Am homopolymer results. Also shown are the cumulative M and M. according to Equation 11.7. The mass of the polymer chains jumps up once the final Am homopolymerization period begins. Reprinted (adapted) with permission from Alb AM, Paril A, Catalgil-Giz H, Giz A, Reed WF. Evolution of composition, molar mass, and conductivity during the free radical copolymerization of polyelectrolytes. J Phys Chem B 2007 111 8560-8566. 2007 American Chemical Society. 

Polymer. The polymer determines the properties of the hot melt variations are possible in molar mass distribution and in the chemical composition (copolymers). The polymer is the main component and backbone of hot-melt adhesive blend it gives strength, cohesion and mechanical properties (filmability, flexibility). The most common polymers in the woodworking area are EVA and APAO. 

At constant PBT/PTMO composition, when the molar mass of PTMO block is >2000, partial crystallization of the polyether phase leads to copolymer stiffening. The properties of polyesterether TPEs are not dramatically different when PTMO is replaced by polyethers such as poly(oxyethylene) (PEO) or poly(oxypropylene). PEO-based TPEs present higher hydrophilicity, which may be of interest for some applications such as waterproof breathable membranes but which also results in much lower hydrolysis resistance. Changing PBT into a more rigid polymer by using 2,6-naphthalene dicarboxylic acid instead of terephthalic acid results in compounds that exhibit excellent general properties but poorer low-temperature stiffening characteristics. 

State-of-the-art polymeric materials possess property distributions in more than one parameter of molecular heterogeneity. Copolymers, for example, are distributed in molar mass and chemical composition, while telechelics and macromonomers are distributed frequently in molar mass and functionality. It is obvious that n independent properties require n-dimensional analytical methods for accurate (independent) characterization of the different structural parameters. 

Bravo, 1984). Hybrids of these systems, where chromatography and electrophoresis are used in each spatial dimension, were reported nearly 40 years ago (Efron, 1959). Belenkii and coworkers reported on the analysis of block copolymers by TLC (Gankina et al., 1991 Litvinova et al., 1991). Two-block copolymers of styrene and f-butyl methacrylate were separated first with regard to chemical composition by TLC at critical conditions, followed by a SEC-type separation to determine the molar masses of the components. 

Statistical and block copolymers based on ethylene oxide (EO) and propylene oxide (PO) are important precursors of polyurethanes. Their detailed chemical structure, that is, the chemical composition, block length, and molar mass of the individual blocks may be decisive for the properties of the final product. For triblock copolymers HO (EO) (PO)m(EO) OH, the detailed analysis relates to the determination of the total molar mass and the degrees of polymerization of the inner PPO block (m) and the outer PEO blocks (n). 

FIGURE 16.10 The SEC chromatogram of a statistical copolymer. Each slice contains macromolecnles of nearly the same size but their molar masses may differ depending on their overall composition and architecture (blockines) hydrodynamic volume of macromolecnles depends on all molecular characteristics of polymer species. 

These materials, however, as a rule exhibit rather broad chemical composition distribution. Block copolymers may contain important amounts of parent homopolymer(s) [232,244,269], In any case, it is to be kept in mind that practically all calibration materials contain the end groups that differ in the chemical composition, size, and in the enthalpic interactivity from the mers forming the main chain. In some cases, also the entire physical architecture of the apparently identical calibration materials and analyzed polymers may differ substantially. The typical example is the difference in stereoregularity of poly(methyl and ethyl methacrylate)s while the size of the isotactic macromolecules in solution is similar to their syndiotactic pendants of the same molar mass, their enthalpic interactivity and retention in LC CC may differ remarkably [258,259]. 

A useful approach to detection in polymer HPLC presents the on-line hyphenation of different measurement principles. For example, an RI detector combined with a UV photometer produces valuable additional information on the composition of some copolymers. Further progress was brought with the triple detection RI plus LALS plus VISCO [313], which is especially suitable for branched macromolecules and the tetra detection UV plus RI plus LALS plus VISCO, which enables characterization of some complex polymer systems, exhibiting a distribution not only in their molar mass and architecture, but also in their chemical composition such as long chain branched copolymers. 

Fig. 8. Copolymer separation. Gradient elution of the mixture of three poly(styrene-c -methyl acrylate) samples on a silica column (600 x 7.5 mm do = 5nm dp= 15 pm). Gradient tetrachloro-methane/methyl acetate (7-35% B in 35 min) flow rate 1 ml/min. The figures at the peaks indicate the composition of the respective copolymer in mol % methyl acrylate. Molar mass values 46.6 — 261 kg/mol 57.3 — 276 77.9 — 302. (From Ref. 381 with permission)...

It is well known that the solubility of polymers depends on their molar mass. This effect can be utilized for the evaluation of molar-mass distributions. With copolymers, solubility is determined by composition and molar mass. Topciev et al. derived the equation ... 

The term cross-fractionation (CF) refers to analyses of distributions in differing directions by means of separation processes. Cross-fractionation is a significant tool for the evaluation of the complex distribution which copolymers normally have with respect to molar mass (MMD) and chemical composition (CCD). The idea of CF implies separation by one parameter and subsequent analysis of the fractions obtained for the distribution of the other parameter through another separating process. 

Consistent notation is adopted throughout this book. Diblock copolymers are written poly(monomer A) poly (monomer B) or PA-PB, where examples of PA and PB are illustrated in Fig. 1.2. Similarly, triblock copolymers are written poly(monomer A)-poly(monomer B)-poly(monomer C) or PA-PB PC. Deuterated blocks are denoted dpoly(monomer A) or dPA. The molar mass of a copolymer is denoted by M, or Af corresponding to the weight- or number-average respectively, and the composition is specified by the volume fraction of one component,/. In solution, the volume fraction of a copolymer is denoted [Pg.3]

The free radical polymerization of DADMAC (M,) with vinyl acetate (M2) in methanol proceeds as a nonideal and nonazeotropic copolymerization with monomer reactivity ratios rx=1.95 and r2=0.35 were obtained [75]. The resulting low molar mass copolymers were reported to be water soluble over their whole range of composition. Modification of the vinyl acetate unit by hydrolysis, ace-talization, and acylation resulted in DADMAC products with changed hydrophilic or polyelectrolyte properties [75]. For the copolymerization of DADMAC and AT-methyl-AT-vinylacetamide (NMVA) a nearly ideal copolymerization behavior could be identified [45]. The application properties of the various copolymer products will be discussed in Sect. 8. 

All potentially molar-mass-dependent quantities have been labelled with a summation index k in Eq. (30), which, in this form, also holds for dilute solutions of mixtures of chemically different species or copolymers with heterogeneity of both chemical composition and degree of polymerization. 

Equation (33) can be further simplified in the case of homopolymers or copolymers with constant chemical composition. It is well known from the literature that Dtis independent of molar mass [11,21,36,37], and the same holds for (dnldck)p>T>Cl kif M is sufficiently high to neglect end-group effects. Under these preliminaries, the molar mass dependence of ak reduces to the concentration of the respective species ak c0>k. 

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