NMR Relaxation of Functionalized Dendrimers

Abstract

Functionalized dendrimers are a novel type of dendritic macromolecules that contain functionalized groups that do not take part in the dendrimer's synthetic cycle. Focusing on the local dynamics of the functionalized dendrimers we study the NMR relaxation by considering the spin-lattice relaxation rate 1/T 1 ) of the 1 and 13 nuclei and the corresponding spectral density. The macromolecules are modeled in the framework that accounts for the local bending rigidity, which is of paramount importance for the NMR relaxation of dendritic structures. We show t h at th e b eh av i or of t h e NMR r el ax ati on of th e f u n cti on al i zed d en d rim er s i s qualitatively different from that of the standard dendrimers manifested through an additional maximum in /T 1 ). The new theoretical picture has allowed us to analyze recent atomistic molecular dynamics simulations of carbosilane dendrimer 2 melts and to elucidate the differences in the high-frequency behavior of their spinlattice relaxation rates from the predictions of the standard dendrimer model.

Local Orientational Mobility of Collapsed Dendrimers

“…This means that the frequency dependencies of NMR relaxation are determined by the topological distance of the segment (to which the observed NMR group belongs) from the periphery ( G–g ) and do not depend on the size of the macromolecule. We observe the same situation in some functionalized dendrimers. , Also, the orientational mobility of semiflexible dendrimers and other hyperbranched structures was theoretically studied in refs and − .…”

“…We observe the same situation in some functionalized dendrimers. 33,34 Also, the orientational mobility of semiflexible dendrimers and other hyperbranched structures was theoretically studied in refs 26 and 35−39.…”

Comparison of Structure and Local Dynamics of Two Peptide Dendrimers with the Same Backbone but with Different Side Groups in Their Spacers

“…This conclusion confirms the possibility of using the coarse-grained models for qualitative study of local orientational mobility in dendrimers. Such models were used in the analytical theory [ 117 , 118 , 119 , 120 , 121 ] and in simulations [ 33 , 122 , 123 , 124 , 125 ].…”

Mechanical relaxation of functionalized carbosilane dendrimer melts

“…Hence one can infer that the contribution of this specific process (FD process) decreases with growing generation. Note that, notwithstanding this FD process being barely detectable in mechanical relaxation experiments, its presence is significant for dielectric 42 and NMR 43 relaxations. Particularly, we established that the FD process appears in NMR relaxation of CSD melts.…”

“…Particularly, we established that the FD process appears in NMR relaxation of CSD melts. 43 It turns out that one chemical bond appearing at each branching point (see Fig. 1) in CSD is enough for the manifestation of the FD process in the NMR relaxation at the intermediate times (albeit not affecting the longer times 42,43 ).…”