Polymers centers

Polymer News, edited by Gerry Kirshenbaum has as a longstanding series featuring academic polymer centers. Those associated with the particular institution are asked to present their programs, aspirations, intents, etc. These are typically well done. Polymer News also features a column on Polymer Education which offers a wide variety of information including booklets, tapes and films related to polymer science, special education (academic and inservice) experiments, polymer science education outside of the USA, recent activity in education committees, featured polymer chemists in academics, reports on education related conferences, etc. 

New York Polymer Center, New York State College of Environmental Science and Forestry, Syracuse, NY 13210... 

Exxon Chemical Company, Baytown Polymers Center, P.O. Box 5200, Baytown, TX 77522. 

Fluoride was found to have a similar, but less pronounced, effect on the MW distribution of polymers made with Cr/silica. An example is shown in Figure 139. Cr/silica catalyst, with and without ammonium bifluoride, was activated at 400 °C and tested for polymerization activity. The addition of fluoride was again found to remove sites producing low-MW polymer. The difference curve is shown, obtained by subtracting the two parent curves after they were normalized by catalyst activity. The addition of fluoride to the catalyst caused a loss of low-MW polymer (centered at about 103 5 or 3200 g mol-1), and a gain of higher-MW... 

Polymer center temperature (Tpc) (2) Polymer side temperature (Tps) (3) Vapor temperature (Tva) (4) Reactor body pressure (Prb) (5) Heat source supply temperature (Tbs) (6) Heat source jacket vent temperature (Ty) (7) Heat source coil vent temperature (Tbc) (8) Heat source supply pressure (Phs) (1) Molecular weight (2) Titrated ends... 

I would like to thank Greg Springstun for experimental help and Dr. Hsien Wang of Baytown Polymer Center for poly (IB-PMS) samples. I would also like to thank Debbie Sysyn for NMR spectra. 

An intense peak is observed for benzidine polymers centered at about 440 nm. As this peak was not present in the monomer, the high values for the susceptibility observed for the polymers may be attributed at least in part to resonance enhancement. Measurements performed by the self-focusing method at the ruby wavelength 694 nm (far from resonance) are about one order lower compared to the values at 532 nm. Time resolved measurements, illustrated in Fig. 3 obtained by delaying one of the interacting beams with respect to the others indicate that the response is fast, of the order of picoseconds, presumably of electronic origin. We also observe a much smaller slow component. 

A simple explanation of this expression is that it is a sum of the translational entropy of the polymer with N monomers per chain (first term in Eq. (1.80)) and the translational entropy of the solvent (second term in Eq. (1.80)). Since the polymers center of mass moves N units at once, its translational entropy is smaller than that of the solvent by a factor of 1 /N. The term proportional to X represents the attractive interaction between the polymer segments. If x is large enough the system will undergo phase separation similar to that of the binary mixture described before. However, because of the factors of 1/A, the critical concentration occurs at small values of the volume fraction if the molecular weight is large = 1/(1 + fN). This is because the entropy... 

This work was funded by the Army Research Laboratory (ARL), Dendritic Polymer Center of Excellence (Contract DAAL-01-1996-02-044). I would like to express my sincere appreciation to Ms L. S. Nixon for preparing the manuscript. 

Thomas C. Yu Senior Staff Engineer, Polyethylene Technology, Baytown Polymers Center, Exxon Chemical Company, Houston, Texas... 

The authors would like to thank the U.S. Army Research Laboratory (ARL/Central Michigan University Dendritic Polymer Center of Excellence), especially Dr. S. McKnight and Dr. B. Fink for financial support of this research (DADD19-03-2-0012) and Linda S. Nixon for manuscript and graphics preparation. 

Langevin dynamics in its above form is useful for sampling the conformations of a polymer, but it does not yield the correct dynamics. To see this we consider a simple polymer chain consisting of N monomers with masses m and total mass M=Nm. Using = f for simplicity the equation of motion of the polymer center of mass is = M or Vcm = A/ K cm- Notc that the net force... 

The "North" effluent comes from the "plastics and polymers" center. An elementary scream (expandable PS, 8 m h ) has already undergone physicochemical purification. 

The constrained distance in A between the electron ring polymer center of mass and the Li ion. 

National Institute of Materials and Chemical Research Japan High Polymer Center 1-1 Higashi, Tsukuba,... 

Polymer Center, University of Lund, Box 118, S-22100 Lund, Sweden... 

Light scattering spectra of random-coil polymers differ from spectra of colloidal particles random coils have observable internal modes. At small q, polymer and colloid internal modes involve distances small relative to so internal modes do not contribute to the time dependence of 5(, t). At large 5(, t) of a rigid particle reflects only center-of-mass motion, because rigid probe particles lack observable internal motions. In contrast, for large q internal modes of flexible molecules involve motions over distances comparable to and thus contribute directly to S q,t). Except at extreme dilution, interactions between polymer chains affect both polymer center-of-mass motion and polymer internal motions. 

The compatibilizer has been prepared by K. Jankova et al. at Danish Polymer Center, Technical University of Denmark. 

---