Monomer composition sample preparation

The above-mentioned regularity was found to be useful (201] to predict the transparency of terpolymer mixtures (acrylonitrile + styrene + a-methyl styrene) of various compositions, which had been studied by Slocombe [128]. He studied the turbidity of sixteen binary and one tetranary blends, prepared via mixing of eight samples corresponding to the particular points of the Gibbs-Roozeboom triangle taken in various combinations. The calculations showed that dispersion erf of all transparent blends was less than its critical value of c meanwhile for all turbid mixtures erf > erfcr. To calulate the dispersion of i-th monomer composition distribution f(t,j) of n-component mixture the following equation was used [201] ... 

We have examined the microstructure of a number of dichlorocarbene adducts of both cis- and trans-polybutadiene using 13C NMR spectroscopy. Samples were prepared in a two phase system where dichlorocarbene was generated by the reaction of either concentrated aqueous or solid alkali metal hydroxide with chloroform in the presence of a phase transfer catalyst (14t). Monomer compositions and sequence lengths were obtained as for true copolymers and were correlated with glass transition temperature and phase morphology. 

Residual Monomers - Compositions to be checked for unreacted monomer were prepared with 1% of hexadecane as an internal standard prior to curing. Following cure, the film was extracted with CCl for two hours in the presence of 0.5% of phenothiazine in a rolling t>ottle. Gas chromagraphic analysis is run as quickly as possible. Samples not immediately analyzed were refrigerated until used. 

In order to form the plastic phase of the semi-IPNs of the first kind and the full IPNs, styrene monomer solutions were prepared containing 0.4% (w/v) dicumyl peroxide and the several quantities of divinylbenzene shown in Table 5.3. To swell in the monomer, a known weight of crosslinked rubber was immersed in the solution at ambient conditions. The ratio of styrene to divinylbenzene actually imbibed was not determined. The duration of imbibing was dependent upon the desired final IPN composition. The swollen polymer then was placed in an airtight container with a saturated styrene atmosphere for approximately 12 hr so that a uniform distribution of monomer could be achieved throughout the sample. Next, the styrene was polymerized thermally at 50°C for a period of 4 days and at lOO C for 1 hr. Finally, the IPN was subjected to a vacuum-drying operation to remove any unreacted monomer. Semi-IPNs of the second kind were prepared by... 

In another work (Prasad et al., 2010a), MIP-carbon composite is prepared via in situ free radical polymerization of a synthetic monomer and subsequent crosslinkage with ethylene glycol dimethacrylate, in the presence of carbon powder and folic acid as template. The detection of folic acid with the MIP fiber sensor was foimd to be specific and quantitative in aqueous, blood serum and pharmaceutical samples, without any problem of nonspecific false positive contribution and crossreactivity. 

The ability to follow comonomer concennation and copolymer composition in real-time allows operators to efficiently determine the end of the reaction. Residual monomer levels are regulated, and in a majority of cases are determined through the HPLC analysis of reactor samples. Reactor sampling, sample preparation, and analysis take time and reduce productivity, particularly if the batch is held in a reactor pending analytical clearance. Additional work that may be required would further reduce productivity. 

While sequence distributions are usually subject to more experimental noise than composition data, this is often outweighed by the greater information content. In principle, reactivity ratios can be estimated from a single copolymer sample. The consistency in reactivity ratios estimated with eqs. 45 and 46 for copolymers prepared with different monomer feed compositions and/or obtaining the same result from cqs. 50 and 51 (4 aab—Ai ab) and cqs. 52 and 53 (r aba-Aiba) arc... 

Samples taken during three different AN/S polymerizations were analyzed chromatographically. Target composition was 70/30 AN/S for all three polymerizations. It is difficult to prepare high nitrile copolymers of styrene because reactivity ratios of the two monomers are very different. This study used continuous addition of monomers to achieve the desired polymer composition. Addition rates were those needed to maintain an excess of acrylonitrile. 

Table I summarizes conditions for the synthesis of two series of PDMAAm-1 -PIBs. The samples are identified by a code consisting of a letter and two numbers the letter (A) denotes the hydrophilic monomer DMAAm, whereas the two numbers indicate the Mn of the starting MA-PIB-MA (divided by 1,000) and the weight percent of PIB in the network (determined by elemental analysis). For example, A-4-26 denotes an amphiphilic network prepared with DMAAm as the hydrophilic moiety, containing a Mn=4,000 MA-PIB-MA, whose composition is 26% PIB.

Beyers et aV° in the Polymer Research Division of BASF-AG used in-line transflectance NIR to monitor methyl methacrylate (MMA) and iV,7V-dimethylacrylamide (DMAAm) monomers in a copolymerization reaction. The work in this paper is of interest as it illustrates an example of calibration development done off-line with a very limited number of prepared calibration samples. The value of the measurement is to control the end properties of the products resulting from the copolymerization reaction. The end properties are related to many parameters including the intramolecular chemical composition distribution (CCD). The... 

Materials. Polymer-bonded sensitizers and their model compounds are shown in Figure 2. Samples 1-5 were prepared by radical copolymerization of corresponding ethylenic monomers using azobisisobutyronitrile as initiator at 70°C in DMF(5) or DMF/H20 (9/1 for 1, 2 and 4 8/1 for 3) (15). Sample 7 was prepared by the same procedure as 6 (16). The copolymer compositions... 

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