Copolymer GPC analysis

Synthesis of block copolymer GPC analysis of the polymerization solution indicated that all the monomer was consumed. The presence of unconsumed initiator was observed. PEG tosylate eluted at 26.2 ml and had UV/ARI of 8000. The chromatogram of a solution of run 1 is given in Figure la. The peak at 24.2 ml corresponds to that of the block copolymer. The peak at 26.2 ml has UV/ARI a. 8000 and should be the unreacted PEG ditosylate. Figure lb shows the elution profile of the of the acetone-washed copolymer and it is free from PEG tosylate. The presence of unconsumed initiator indicated slow initiation. Also, since the two ends of PEG tosylate are identical in reactivity by random statistics (12) we expect the copolymer to be a mixture of ABA type trlblock (initiation at both ends) and AB type dlblock (initiation at one end) copolymers. This was observed, as shown by the solid line of Figure 2 when the copolymer was eluted through a different combination of columns. The peak at 24.0 ml corresponds to the triblock copolymer and the peak at 25.4 ml corresponds to the dlblock copolymer. 

A commercially available poly(ethylene-co-glycidyl methacrylate) [p(E-co-GMA)] poljmier was transformed into an ATRP macroinitiator (163) by reacting the p(E-co-GMA) with either 2-bromoisobutyric acid or chloroacetic acid to prepare a backbone with multiple initiator sites. The resulting polymer was used as a macroinitator for ATRP of St and MMA (Fig. 15). The consumption of both monomers increased with time, as did the weight percent of the side chains in the copolymer. GPC analysis of the cleaved pSt side chains showed a linear increase of molecular weight with monomer conversion, and M IM < 1.4 (163). 

Fig. 3. GPC analysi.s of EGA homopolymer, 50 50 ECA/DEMM copolymer, and DEMM homopolymer.

GPC analysis of homo- and copolymers of acrylic esters ( acrylic will be used throughout this chapter to refer to both acrylic and methacrylic) is quite straightforward. A representative set of conditions is... 

With regards to the copolymerization, a recent kineuc study by Gruber and KneU (10 has indicated that styrene n-butyl methacrylate obeys the cla ical kinetic theory with regards to composition and sequence length to complete conversion. This theory is applied to high conversion to charau terize copolymer samples for GPC analysis. 

Some experimental data that were obtained through a series of polymerization studies with a methacrylate-terminated MACROMER with vinyl chloride are shown in Figure 12. The Alfrey-Goldfinger equation was used to calculate the copolymer composition for comparison to the actual copolymer composition as estimated from GPC analysis. A reasonably close agreement was achieved of the actual and the theoretical copolymer compositions, which indicates that the r values are in the region of r2 = 10 and r2 = 0.1. 

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. 

Biphenyl-phosphole copolymer 65 is isolated as an air-stable and soluble powder exhibiting a rather high molecular weight (Mw = 16 000 Mn = 6200) according to gel permeation chromatographic (GPC) analysis. Although multinuclear magnetic resonance spectroscopy and elemental analysis support the proposed structure, the presence of a small number of diene defects is very likely. Polymer 65... 

Solutions of Biomer were obtained from Ethicon Inc. Biomer is poly (ether polyurethane) which contains urea linkage in the hard segment according to our IR analysis (19). Films of Biomer were cast on clean glass plates by diluting the polymer solution in dimethyl acetyl-amide. The films were dried in a vacuum oven at 50°C for 24 hr. The final film thickness was around 125/a. GPC analysis showed that the content of oligomers in Biomer was also negligible. Kel-F82, which is a copolymer composed of chlorotrifluoroethylene (97%) and vinylidene fluoride (3% ), was obtained from the 3M Company. 

A Schlenk tube was charged with di-[di-(trimethylsilyl)amine]stannate (0.05 mmol), d,l-lactide (39.3 mmol), glycolide (13.1 mmol), and 15 ml of mesitylene and then heated to 160°C for 3 hours. H-NMR analysis indicated that the conversion was complete and that the copolymer consisted of 75% d,l-lactide and 25% glycolide. GPC analysis indicated the product had aM of77,500 daltons with a polydispersity of 1.67. 

Likewise, for the semibatch operation, the influence of monomer was seen in the differences between macro- and miniemulsion feeds. For extremely water-insoluble monomers, the miniemulsion-feed mode lessens the departure of the copolymer composition from the feed composition during semi-starved semibatch polymerization. However, this is accomplished by simultaneously broadening the PSD. Results from the GPC analysis indicated that the polymers with lower molecular weight and broader distribution were formed in the semibatch process, in contrast to the batch run. 

This procedure is carried out in exactly the same way as described in Protocol 2. However, in this approach, once complete conversion ofthe initial monomer feed has been attained (as determined by GPC analysis) a second monomer is added to the reactor flask. Since the polymerization exhibits living characteristics, active polymer chain ends still exist in the monomer starved flask and further addition of another monomer enables the polymerization to continue, therefore producing an AB block copolymer. 

Surprisingly, the addition of TBA to a solution of living poly-PEMA also leads to the quantitative formation of a block copolymer as Is shown by GPC analysis (Figure 4). This proves that the rate constant of the Initiation for the TBA polymerization by the PEMA azlrldlnlum Ion Is of the same order of magnitude as the homopropagation constant for TBA or k2i 1 11 ... 

Figure 3. GPC analysis of poly-TBA-poly PEMA block-copolymer (A) and of the poly-TBA used as the macromolecular initiator(B).

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