Molecular Weight Polymethyl Methacrylate

Figure 8. DRI and viscometer chromatograms for a high molecular weight polymethyl methacrylate sample.

The main experimental techniques used to study the failure processes at the scale of a chain have involved the use of deuterated polymers, particularly copolymers, at the interface and the measurement of the amounts of the deuterated copolymers at each of the fracture surfaces. The presence and quantity of the deuterated copolymer has typically been measured using forward recoil ion scattering (FRES) or secondary ion mass spectroscopy (SIMS). The technique was originally used in a study of the effects of placing polystyrene-polymethyl methacrylate (PS-PMMA) block copolymers of total molecular weight of 200,000 Da at an interface between polyphenylene ether (PPE or PPO) and PMMA copolymers [1]. The PS block is miscible in the PPE. The use of copolymers where just the PS block was deuterated and copolymers where just the PMMA block was deuterated showed that, when the interface was fractured, the copolymer molecules all broke close to their junction points The basic idea of this technique is shown in Fig, I. 

Polymerization of t-butyl methacrylate initiated by lithium compounds in toluene yields 100% isotactic polymers 64,65), and significantly, of a nearly uniform molecular-weight, while the isotactic polymethyl methacrylate formed under these conditions has a bimodal distribution. Significantly, the propagation of the lithium pairs of the t-Bu ester carbanion, is faster in toluene than in THF. In hydrocarbon solvents the monomers seem to interact strongly with the Li+ cations in the transition state of the addition, while the conventional direct monomer interaction with carbanions, that requires partial dissociation of ion-pair in the transition state of propagation, governs the addition in ethereal solvents. 

Determined by GPC with polymethyl methacrylate (PMMA) as the reference standard. "Molecular weight distributions. 

The column set was calibrated with a series of polystyrene stan rds with weight average molecular weights (Mw) between 2X10 and 4.1X10°. The standards were supplied by Pressure Chemical Co., Pittsburgh, Pa. and ArRo Laboratories, Inc., Joliet, 111. Other systems used in this work included the NBS-706 polystyrene standard and an emulsion polymerized polymethyl methacrylate sample. 

Polymethyl Methacrylate. Table 4 shows the results obtained for three commercially available polyraethyl methacrylate samples. Again the molecular weight averages obtained with SEC/Viscometry are in good agreement with the nominal values and the K and o values are self-consistent and in excellent agreement with the literature values.(40)... 

The molecular weight of samples tested ranged from 4 x 104 to some 40 x 104. In this connection it should be mentioned that two polymethyl methacrylate samples haviqg 16.5 x 104 and 41.2 x 104, coded PMA-3 andPMA-2, respectively, showed a strong molecular-weight dependence of Rf even under the condition that adsorption mechanism was certainly operative15,21. ... 

Fig. 14. Molecular-weight dependences of Rf observed for polymethyl methacrylate samples, coded PMA-3 and PMA-2 (left and right spot in each chromatogram, respectively), using three different but equi-ehiotropic binaries, (a) benzene + acetone, (b) isopropyl acetate + methyl formate and, (c) ethyl acetate + methyl acetate...

Fig, 5.3. Viscosity at various concentrations and molecular weights in the low to moderate concentration range. Polystyrene-decalin and polymethyl methacrylate-xylene are theta or near-theta systems the remainder are good solvent systems (121,177). Note that the c[i/] reduction is somewhat better in theta solvents, and that the Martin equation [Eq. (5.9)], which would give a straight line in the figure, is a somewhat better representation for... 

Fig. 5.11. Initial slopes tanaof extinction angle curves vs. parameter = M[rf]ridRT for infinitely dilute solutions of various fractions of polymethyl methacrylate in tetrabromo-ethane according to Tsvetkov and Budtov (192). For each fraction x is varied by changing the temperature of measurement, i.e. the factor r]0IT. The molecular weights of the fractions are I/I.. . 15.2 x 10, A. .. 12.4 x 10, II. .. 11.0 x 10 , III... 5.8 x 10 , IV. .. 3.7 x 10 and V. .. 1.6 x 10 ...

In Fig. 5.11 some results of Tsvetkov and Budtov (192) are reproduced. These results were obtained on narrow fractions of polymethyl methacrylate of rather high molecular weights. These molecular weights are given in the caption to the figure. 

It was also described that some common vinyl polymers, such as polymethyl methacrylate prepared with benzoyl peroxide, are able to initiate a further polymerization if heated in the presence of a second monomer [158). These phenomena must be interpreted by the existence of peroxide links inside the polymethyl methacrylate chain [229). Indeed any activity is destroyed on prolonged heating and this polymer can be used for initiating the polymerization of styrene. However the relative length of the sequences and the molecular weight of the product before and after copolymerization have not yet been determined. 

In the case of styrene the polymer contains at both ends a carboxyl group (chain termination by coupling), while polymers characterized by a termination reaction by disproportionation (polyvinyl acetate, polymethyl methacrylate) contain only one carboxyl end group. The carboxyl groups in these polymers were transformed to acid chlorides and coupled with a diol, e.g. 1,6-hexanediol. The comparison of the molecular weight of the polymers before and after condensation permits to elucidate the... 

Baxendale, J. H., S. Bywater and M. G. Evans Relation between molecular weight and intrinsic viscosity for polymethyl methacrylate. J. Polymer Sci. 1, 237 (1946). 

PC PE PES PET PF PFA PI PMMA PP PPO PS PSO PTFE PTMT PU PVA PVAC PVC PVDC PVDF PVF TFE SAN SI TP TPX UF UHMWPE UPVC Polycarbonate Polyethylene Polyether sulfone Polyethylene terephthalate Phenol-formaldehyde Polyfluoro alkoxy Polyimide Polymethyl methacrylate Polypropylene Polyphenylene oxide Polystyrene Polysulfone Polytetrafluoroethylene Polytetramethylene terephthalate (thermoplastic polyester) Polyurethane Polyvinyl alcohol Polyvinyl acetate Polyvinyl chloride Polyvinyl idene chloride Polyvinylidene fluoride Polyvinyl fluoride Polytelrafluoroethylene Styrene-acrylonitrile Silicone Thermoplastic Elastomers Polymethylpentene Urea formaldehyde Ultrahigh-molecular-weight polyethylene Unplasticized polyvinyl chloride... 

The pigmentation of Polymethyl Methacrylate (PMMA) and ultrahigh-molecu-lar-weight polyolefins presents familiar difficulties. Due to the high difference in viscosity between the pigment concentrate and these polymers, it is sometimes necessary to use special masterbatches based on high-molecular-weight carriers. 

Figure 4.29 Loss tangent versus frequency for three low-molecular-weight organic glass-forming viscous liquids with viscosities around 10 P hydrox-ypentamethyl flavan (HPF) at 16°C, glycerol sextol phthalate (GSP) at 26°C, and 2-phenyl-3-j3-tolylindanone (PTI) at 20°C. Also shown are data for polymeric glasses polymethyl methacrylate (PMMA), and polystyrene (PS) at room temperature. (From Benbow and Wood 1958, with permission of the Royal Society of Chemistry.)...

Data relating intrinsic viscosity and molecular weights are not available for any of the polymers of the dialkyl itaconates. Polymethyl methacrylate constants have been used to estimate molecular weights for the polydiethyl itaconates but the exactness of such an approximation is difficult to judge. While exact molecular weights cannot be... 

Initiator concentration has a more pronounced effect upon the molecular weights of MMA polymers than those from DMI. This is shown in Fig. 2 where log vs. log [/] is plotted for benzoyl peroxide-initiated bulk polymerization of each monomer at several temperatures and low conversions. Under comparable conditions the intrinsic viscosities of pol5miefhyl methacrylate are 5—10 times those of polydimethyl itaconate. While a 10-fold decrease in initiator concentration results in a 100% or greater increase in intrinsic Auscosity of polymethyl methacrylate, that... 

Polysulfone membranes were prepared from 12.5, 13.75, and 15% (wt. %) polysulfone solution in dimethylformamide and formed on the surface of porous, sintered polymethyl methacrylate bars. An effective surface of each membrane was 49.2 cm. The effect of some casting parameters (composition and the temperature of the casting solution, time of solvent evaporation) and the pressure applied on the transport and separation properties of the membranes were analyzed. The experiments were carried out in a 1.2 dm pressure apparatus with continuous circulation of the permeate between feeding tank and the apparatus. It was found that membranes cast from 12.5% polysulfone solution of a temperature of 298 K with no solvent evaporation displayed the best properties. After 160 hours of operation at 0.18 MPa, the membranes in question showed an ability of a 97 to 99% rejection of 781.2 molecular-weight dye. The volume flux of the dye solution varied from 0.6 to 0.8m /m per day. 

Materials. A commercial grade polymethyl methacrylate (PMMA, PRD-41) was obtained from the Rohm and Haas Company. The weight-average molecular weight of the polymer and polydispersity, as determined by gel permeation chromatography, were 200,000 and 2.35, respectively. The solvents used (methanol, acetone, methyl... 

The X-ray masks consist of a thin membrane (e.g., 3-pm titanium or 30-pm beryllium) together with absorbers consisting of X-ray opaque gold layers that are more than 10 pm in thickness in order to achieve the required mask contrast. Within the irradiated sections of the resist layer, the polymer chains are destroyed reducing their molecular weight. In most experiments polymethyl methacrylate (PMMA) is used as the X-ray resist. 

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