Random copolymer, definition

Random copolymer—Distribution of the monomer units does not follow any definite sequence. These are produced in bulk, aqueous, suspension, or emulsion using free radical initiators of the peroxide type or redox systems. 

It is important to recognize that the following analytical methods essentially determine EO-PO ratio ( H NMR, IR, cleavage methods) or even simply alkylene oxide content (compleximetric methods) of the analyte, and as such are not specific quantitative or qualitative methods for poloxamers, since EO-PO copolymers of a different structure (for instance, random copolymers, or PO-EO-PO block copolymers) may respond to the methods in a way indistinguishable from poloxamers. The principal technique that permits definitive identification of a sample as a poloxamer is C NMR, which allows structural details, such as the distribution of EO and PO units along the polymer chain, to be elucidated [10]. 

In this review, synthesis of block copolymer brushes will be Hmited to the grafting-from method. Hussemann and coworkers [35] were one of the first groups to report copolymer brushes. They prepared the brushes on siUcate substrates using surface-initiated TEMPO-mediated radical polymerization. However, the copolymer brushes were not diblock copolymer brushes in a strict definition. The first block was PS, while the second block was a 1 1 random copolymer of styrene/MMA. Another early report was that of Maty-jaszewski and coworkers [36] who reported the synthesis of poly(styrene-h-ferf-butyl acrylate) brushes by atom transfer radical polymerization (ATRP). 

This article reviews the phase behavior of polymer blends with special emphasis on blends of random copolymers. Thermodynamic issues are considered and then experimental results on miscibility and phase separation are summarized. Section 3 deals with characteristic features of both the liquid-liquid phase separation process and the reverse phenomenon of phase dissolution in blends. This also involves morphology control by definite phase decomposition. In Sect. 4 attention will be focused on flow-induced phase changes in polymer blends. Experimental results and theoretical approaches are outlined. 

As mentioned above for copolymer based blends the quantities e and r in definitions (9) have to be replaced by number-averaged quantities . For a blend of a homopolymer A and a random copolymer B, P(CpD, p), comprising segments of type C and D with mole fractions p and (1 — p), respectively, the generalization of the parameters can be done along the same lines as sketched in Appendix III. It is useful to introduce the following notations ... 

So far in our discussion of micros tincture, we have considered homopolymers. To some degree, however, there is an element of semantics involved in our definition. Is a branched polyethylene a true homopolymer or should it be considered a copolymer of ethylene and whatever units comprise the branches Here our concern is real copolymers, those synthesized from two (or more) distinct monomers. The simplest possible arrangements are shown in Figure 2-22 and are self-explanatory. But, as we will see, real life is more complex. True random copolymers are rare and in most cases there are tendencies to blockiness or alternating arrangements. There are also graft copolymers, but we will discuss all this in more detail when we consider copolymerization. 

The properties of random copolymers can be estimated by using weighted averages for all extensive properties, and the appropriate definitions for the intensive properties in terms of the extensive properties. Let lrq, m2,. .., mn denote the mole fractions (see Section l.D) of n different types of repeat units in a random copolymer. [The most common random copolymers have n=2. Terpolymers (n=3) are also often encountered.] The n mole fractions then add up to one, and the extensive properties of a random copolymer can be estimated by using mole fractions as weight factors ... 

The formal definition of a copolymer is a polymer derived from more than one species of monomer. The copolymer with a relatively random distribution of the different mers or repeating units in its structure is commonly referred to as a random copolymer. Representing two different mers by A and B, a random copolymer can be depicted as... 

Definition Random copolymer produced by interaction of 17 moles ethylene oxide with 6 moles of propylene oxide Toxicology TSCA listed... 

Figure 3.14). Values of exhibit only one transition, which systematically moves down the temperature scale as the NBR-40 content is increased. Further, the glass transition for the NBR-40 blends assumes a sharpness characteristic of homopolymers or random copolymers. Clearly an increase in the AN content of NBR results in an increased compatibility with PVC. However, as shown earlier by electron microscopy, a definite degree of phase separation still exists for all of these compositions. 

Definition Random copolymer produced by interaction of 17 moles ethylene oxide with 6 moles of propylene oxide Toxicology TSCA listed Uses Solvent in cosmetics lubricant for antiperspirants emollient bodying agent lubricant for textile spin finishes intermediate for prep, of resins, plasticizers, modifiers, and surfactants demulsifier food-pkg. adhesives, animal glues defoamer in food-contact paper/paperboard... 

Definition Random copolymer produced by interaction of 18 moles ethylene oxide with 4 moles of propylene oxide Uses Solvent in cosmetics Manuf./Distrib. Aldrich http //www.sigma-aldrich.com, Fluka http //www.sigma-aldrich.com, Sigma PEG/PPG-23/50 copolymer CAS 9003-11-6 (generic)... 

Ciassification Propylene copolymer Definition Amorphous or crystalline random copolymer... 

See references (62 and 70) for definition of types of isomorphism. Random copolymers of ethylene-vinyl alcohol ... 

The definitions above of statistical and random copolymers are idealized. In reality, significant nonrandomness may exist. Since the physical and mechani-... 

In trace I is seen the NMR spectrum of the nearly random copolymer used as a starting material, while traces II through V apply to the copolymers resulting from the second hydrolysis step. The reaction times increase from trace II to V. The triads AgEgA and BsAgB are present in strikingly small amounts only, the monomer distribution has therefore a definite tendency toward blockiness. 

Fig. 7 Definition of coarse-grained repeat units (symbolized by circles) for the 1,4-polybntadiene chain. The atomistic model is an united abun model of a random copolymer of 45% cis and 55% trans content, without vinyl units. Bmid lengths ate constrained ( = 1.53 A for the CH2-CH2 bond, i = 1.5A for the CH2-CH bond and 1.34A fiuthe CH-CH bond). From Strauch et al. [117]...

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