摘要:

AbstractTwo‐dimensional wideline separation (WISE) NMR spectroscopy was employed to investigate the microscopic domain structure of an ethylene‐containing acid ionomer, poly(ethylene‐co‐methacrylic acid). Crystallinities were determined from deconvolution of the proton dimension lineshapes, and domain sizes were computed from proton spin diffusion behavior. The time‐scale for spin diffusion between the acid groups and the amorphous regions is less than 1 ms, because the methacrylic acid groups are situated in the amorphous domains. On the other hand, communication between amorphous and crystalline domains requires several milliseconds, consistent with crystalline domain sizes ofca4 nm. The presence of intermolecular hydrogen‐bonded cross‐linking is clearly detected by the broad proton linewidth associated with the rigid methacrylic acid groups. It is shown that imbibed hexadecane, which strongly plasticizes the amorphous regions of the copolymer, has little effect on crystallinity, crystalline domain sizes or cro

ISSN:0749-1581    

DOI:10.1002/mrc.1260321312

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractSeveral small‐molecule hosts form clathrates or inclusion compounds (ICs) with polymers. In these polymer‐ICs the guest polymer chains are confined to occupy narrow channels in the crystalline matrix formed by the host. The walls of the IC channels are formed entirely from the molecules of the host, and they serve to create a unique solid‐state environment for the included polymer chains. Each polymer chain included in the narrow, cylindrical IC channels (ca5.5 Å in diameter) is highly extended and also separated by the host matrix channel walls from neighboring polymer chains. The net result is a solid‐state environment where extended, stretched (as a consequence of being squeezed) polymer chains reside in isolation from their neighbors inside the narrow channels of the crystalline matrix provided by the small‐molecule host. Comparison of the behavior of isolated, stretched polymer chains in their crystalline ICs with observations made on ordered, bulk samples of the same polymer are beginning to provide some measure of the contributions made by the intrinsic nature of a confined polymer chain and the pervasive, cooperative, interchain interactions which can complicate the behavior of bulk polymer samples. Just as dilute polymer solutions at the θ temperature have been effectively used to model disordered, bulk polymer phases (both glasses and melts), polymer‐ICs may be utilized to increase our understanding of the behavior of polymer chains in their ordered, bulk phases as found in crystalline and liquid‐crystalline samples. Solid‐state NMR observations of polymer‐ICs can provide detailed conformational and motional information concerning the included, stretched and isol

ISSN:0749-1581    

DOI:10.1002/mrc.1260321313

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractHigh‐resolution13C cross‐polarization/magic angle spinning (CP/MAS) spectra of the crystalline component of quench‐cooled isotactic polypropylene (iPP) were obtained by using a pulse sequence that incorporates a delay period with a reduced spin locking field prior to cross‐polarization, thus exploiting the differences in1HT1prelaxation times between the various phases. The spectra of samples annealed at high temperature have resolved splitting, ranging between 0.2 and 1.1 ppm, for all carbon resonances. The methyl resonance is composed of three resolved peaks whose relative areas, as obtained through peak deconvolution, depend on the anneal temperature. Large changes in these peak areas coincide with an exothermic transition observed by differential scanning calorimetry. The spectra of the interfacial and amorphous phases, obtained by subtraction, indicate a reduction in the amorphous content at anneal temperatures>100°C while the interfacial component appears to increase owing to recrystallization and the formation of more amorphous/crystal in

ISSN:0749-1581    

DOI:10.1002/mrc.1260321314

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe 400 MHz proton NMR spectra of butyl acrylate (BA)—methyl methacrylate (MMA) copolymers prepared by free radical polymerization in solution at 323 K were used for the determination of the reactivity ratios. The reactivity ratiosrMandrBcalculated by the error‐in‐variables method are 2.279 and 0.395, respectively. The methoxy region of the MMA proton signal resonance was found to be sensitive for MMA‐centred sequences and a new assignment is proposed. The coisotacticity parameter σBMwas calculated using a non‐linear least‐squares procedure with relative error estimation based on the new assignment and was found to be 039. The carbon‐13 NMR spectra of the BA‐MMA copolymers, in particular the carbonyl signal resonances, are sensitive for MMA‐and BA‐centred configurational sequences. The same assignment is used as for the ethyl acrylate—methyl

ISSN:0749-1581    

DOI:10.1002/mrc.1260321315

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0749-1581    

DOI:10.1002/mrc.1260321301

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY