Molecular weight analysis methacrylates

The high sensitivity of the viscosity detector to the high molecular weight fractions is demonstrated in the analysis of a sample of very high molecular weight polyCmethyl methacrylate) shown in Figure 8. A shoulder at 3,000,000 molecular weight detected by the DRI becomes a peak when detected by the viscometer detector. 

The presence of two hydroxyl groups per molecule in poly-(methyl methacrylate) and in polystyrene, each polymerized in aqueous media using the hydrogen peroxide-ferrous ion initiation system, has been established " by chemical analysis and determination of the average molecular weight. Poly-(methyl methacrylate) polymerized by azo-bis-isobutyronitrile labeled with radioactive has been shown to... 

GTP was employed for the synthesis of block copolymers with the first block PDMAEMA and the second PDEAEMA, poly[2-(diisopropylamino)e-thyl methacrylate], PDIPAEMA or poly[2-(N-morpholino)ethyl methacrylate], PM EM A (Scheme 33) [87]. The reactions took place under an inert atmosphere in THF at room temperature with l-methoxy-l-trimethylsiloxy-2-methyl-1-propane, MTS, as the initiator and tetra-n-butyl ammonium bibenzoate, TBABB, as the catalyst. Little or no homopolymer contamination was evidenced by SEC analysis. Copolymers in high yields with controlled molecular weights and narrow molecular weight distributions were obtained in all cases. The micellar properties of these materials were studied in aqueous solutions. 

Philippova and Starodubtzev have also extensively studied the complex-ation behavior of polyacids and PEG, especially, the system of crosslinked of poly(methacrylic acid) and linear poly(ethylene glycol) (Philippova and Starodubtzev, 1995 Philippova et al., 1994). They observed that decreasing the molecular weight of PEG from 6000 to 1500 resulted in its slower diffusion into the swollen network of PMAA, and a drastic decrease in both the stability and equilibrium composition of the intermacromolecular complex. Analysis of dried polymer networks of PMAA with absorbed PEG chains by FT-IR spectroscopy revealed the presence of two types of hydrogen bonded structures (1) dimers of methacrylic acid at absorption frequency of 1700 cm-1 and (2) interpolymer complexes of PMAA and PEG at 1733 cm-1. In addition, they also suggested as a result of their studies, that the hydrogen bonded dimer of PMAA forms preferentially to the intermacromolecular complex between the PMAA network and PEG chains. 

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. 

The polymerization of methyl methacrylate is retarded by p benzo-quinone. Kinetic analysis (38) showed that the molecular weight and rate data could be interpreted if... 

Our kinetic work (10) showed that the small molecule radical produced by chain transfer with monomer had to be a stable radical. This was confirmed in the present paper by analysis of the isotope effect on the bulk polymerization rates. The isotope effect on molecular weights and rates unequivocally showed that almost 100% of the chain transfer involved the vinyl hydrogen. There is some evidence in the literature to support the idea of a stable vinyl radical. Phenyl acetylene acts as a retarder when copolymerized with styrene or methyl methacrylate (25). Thus the phenyl vinyl radical is very stable compared to the growing styryl or methacrylyl radical. 

The available data from emulsion polymerization systems have been obtained almost exclusively through manual, off-line analysis of monomer conversion, emulsifier concentration, particle size, molecular weight, etc. For batch systems this results in a large expenditure of time in order to sample with sufficient frequency to accurately observe the system kinetics. In continuous systems a large number of samples are required to observe interesting system dynamics such as multiple steady states or limit cycles. In addition, feedback control of any process variable other than temperature or pressure is impossible without specialized on-line sensors. This note describes the initial stages of development of two such sensors, (one for the monitoring of reactor conversion and the other for the continuous measurement of surface tension), and their implementation as part of a computer data acquisition system for the emulsion polymerization of methyl methacrylate. 

A characterization of the obtained samples showed that each molecule contains one ester function, one phenyl ring and one methacrylic unsaturation. The accessible molecular weight range is broad. However, to ensure a high accuracy of the techniques used for the characterization of these macromonomers (NMR, UV, IR spectrometry, vapor pressure osmometry, double bond analysis) and to employ the latter in graft copolymer synthesis molecular weights in the range 1000 to 10000 g mol-1 have been preferred 46). 

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