SPP gel

Molecular Conformation of sPP gel. Figure 27 shows the DD/MAS 13C NMR spectrum of sPP gel. This spectrum was obtained by a single-pulse sequence (tt /2—FIDdd-tt)ii with the repetition time ty more than 5 times the longitudinal relaxation time Tic. Hence, this spectrum reflects the thermal equilibrium state of the gel. For comparison, the spectrum of the bulk ttgg crystal of this sample... 

Phase structure. It was confirmed in the previous section that the bulk iPP crystal consists of three phases the crystalline, noncrystalline amorphous phase and crystalline-amorphous interphase. Hence, it is also assumed that the bulk sPP crystal forms a three-phase structure in a similar manner. The question here is whether the sPP crystal involves such a phase structure in forming a gel or not In order to study this problem, we have analyzed 13C NMR spectra of the sPP gel. The noncrystalline contributions to each resonance of CH2, CH and CH3 carbons in the DD/MAS 13C NMR spectrum of the gel can be seen, as indicated by the arrows in Fig. 27, where their assignment as noncrystalline resonances was confirmed by the spin-lattice and spin-spin relaxation times as described above with relation to the results in Table 13. We carried out the line-decomposition analysis of the resonance lines of the methine and methyl carbons, since these resonances are most pertinent for the present purpose because of the simplicity of the spectral shape. 

Phase structure. It was confirmed in the previous section that the bulk iPP crystal consists of three phases the crystalline, noncrystalline amorphous phase and crystalline-amorphous interphase. Hence, it is also assumed that the bulk sPP crystal forms a three-phase structure in a similar manner. The question here is whether the sPP crystal involves such a phase structure in forming a gel or not In order to study this problem, we have analyzed NMR spectra of the sPP gel. 

Non o the analyzed samples showed the presence of gels and the low M /M and M /M ratios of the highest molecular weight sample (table I) indicate that the SPP is not susceptible to m.w.d. broadening. 

R. Sen and C. M. Hepper, Characterization of vesicular-arbu.scular mycorrhizal fungi (Glomus spp.) by. selective enzyme staining following polyacrylamide gel electrophoresis. Soil Biol. Biochem. 18 29 (1996). 

According to gel permeation chromatography (GPC) data, the molecular weight of SPP increased after X-ray exposures both in air and in vacuum. The elution profiles in both cases were very similar, indicating that the coupling of APSQ and DNQ or the condensation of APSQ occurs irrespective of the ambient. 

PolyHIPE has found a successful application in the field of solid phase peptide synthesis (SPPS), where the highly porous microstructure acts as a support material for a polyamide gel [134]. The polystyrene matrix is functionalised to give vinyl groups on its internal surfaces, and is then impregnated with a DMF solution of N, JV -dimethylacrylamide, acryloylsarcosine methyl ester, crosslinker and initiator. Polymerisation grafts the soft gel onto the rigid support, giving a novel composite material (Fig. 16). 

We studied the structure of bulk-crystallized isotactic polypropylene in the previous section, in this section we will examine the gel structure of syndiotactic polypropylene (sPP) [25]. Many crystalline polymers form a gel from the con-... 

Fig. 27. Equilibrium DD/MAS 13C NMR spectrum of sPP/o-dichlorobenzene gel (13.6 wt%), obtained by a n/2 single pulse sequence with a repetition time of 300 s. In the lower part the equilibrium spectrum of the bulk sPP crystal in ttgg form is shown for reference. The arrows indicate the resonance of the amorphous component of each carbon...

Since two resonance lines at 39.0 and 47.7 ppm that correspond to those observed in the ttgg form and a resonance line at 49.0 ppm that corresponds to that in the tttt form are recognized in the gel spectrum, a coexistence of these two forms in the gel might be supposed. In an attempt to determine the possibility of the coexistence of the two forms in the gel, we measured the IR spectrum that is sensitive to the molecular conformation. The number of normal vibrational modes depends sensitively on the molecular conformation based on the selection rule of the symmetry species. Kobayashi et al. confirmed the vibrational modes assignable to the ttgg conformation in the IR spectrum for the gel from a sPP/carbon disulfide system [117]. However, since we used o-dichlorobenzene as solvent, we examined whether the gel structure depends on the solvent. 

Fig. 29. IR spectra of the tttt and ttgg bulk crystals and sPP/o-dichlorobenzene gel (13.6 wt%). The spectrum of the gel represents only the contribution from the sPP polymer that was obtained by subtracting the contribution from the solvent...

Fig. 30. Line shape analyses of the resonance lines of methine and methyl carbons in sPP/o-dichlorobenzene gel. A, B, and C indicate the crystalline, amorphous, and crystalline-amorphous interfacial components, respectively. (This figure was obtained by revising Fig. 7 in Ref. 25 whose horizontal chemical shift axis was somewhat shifted)...

Phase Structure as Revealed from the Mobility of the Solvent. The phase structure of the sPP crystal in the gel form, which was elucidated by the line-decomposition analysis of the DD/MAS 13C NMR spectrum, will reflect on the mobility of the solvent in the gel. The mobility of the solvent can be examined by the longitudinal relaxation of resonance lines assigned to the carbons of the solvent. Figure 31 shows the longitudinal relaxation for the line at 130 ppm of the o-dichlorobenzene. The open circles indicate the data of the pure solvent and the closed ones those of the solvent in the gel. As can be seen, the relaxation of the pure solvent evolves exponentially with a Tic of 3.0 s, whereas that of the solvent in the gel evolves nonexponentially. This indicates that there are some solvent molecules in the gel that differ in their mobility. We assume here that the longitudinal relaxation of each component of the solvent evolves exponentially. Then the longitudinal relaxation of the total solvent follows the relationship ... 

As can be seen from the Table 15, 70 and 30% of the solvent are respectively in the bound and free state. The mass fractions of the bound and free solvents are in rough accordance with those of the crystalline-amorphous interphase and the amorphous phase in the two noncrystalline phases of the polymer. This result suggests that the solvent exists in the two noncrystalline phases of the polymer, as the bound solvent in the crystalline-amorphous interphase and as the free solvent in the amorphous phase, leaving the crystalline phase pure. It is concluded that the sPP/o-dichlorobenzene gel involves three phases, (1) the pure crystalline... 

It has also been proposed that the presence of endophytes can alter the usual suite of secondary metabolites of plants. For example, whilst Murraya spp. have been reported to produce indole and carbazole alkaloids, the Brazilian M. paniculata did not [25]. An endophytic Eupenicillium sp. was isolated from surface-sterilized leaf material of the Brazilian M. paniculata and subsequently cultured on white corn. The Eupenicillium sp. produced hydrophobic spiroquinazoline alkaloids that were separated using silica gel column chromatography and preparative gel-filtration... 

Cocolin, L., Manzano, M., Cantoni, C., Comi, G. (2000). Development of a rapid method for the identification of Lactobacillus spp. isolated from fermented Italian sausages using a polymerase chain reaction-temperature gradient gel electrophoresis. Lett. Appl. Microbiol., 30, 126-129. 

Besides the classical polymer introduced by Merrifield (1%-crosslinked chloromethylated polystyrene), a broad variety of polymeric supports is available for SPPS and some of the most popular resins are summarized in Table 1. The chemical structures of some selected resins are presented in Figure 1 and electron micrographs of several examples are displayed in Figure 2. In addition to the solid supports listed in Table 1, there are several other carriers used in peptide synthesis such as the gel-type and macroporous poly(meth-acrylates), coated surfaces like polystyrene films on polyethylene (PEt) sheets, polystyrene-coated polyethylene or polytetrafluoroethylene, and modified glass surfaces. (For recent reviews on polymeric carriers see refs . )... 

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