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oai:figshare.com:article/34033317 2026-09-30T15:04:11Z category_1 category_4 category_7 category_12 category_13 category_14 category_16 category_873 category_734 category_62 portal_63 item_type_6 month_year_09_2026

Stoichiometry-Dependent Structural Defects in Low-Generation PAMAM Dendrimers Chun T. Huang (25144563) Cesar L. Petzhold (1788973) Biophysics Biochemistry Medicine Cell Biology Genetics Molecular Biology Physiology Chemical Sciences not elsewhere classified Biological Sciences not elsewhere classified Marine Biology modified carothers equation linear polymer standards identical analytical conditions bridged amide environments dependent structural defects reducing structural heterogeneity generation pamam products bridged species (< 114 ), consistent interpreted cautiously due complementary analytical techniques compare sample heterogeneity theoretical molecular weights 1 </ sup generation species complementary techniques minimizing defects z </ trend consistent product heterogeneity f </ derived molecular dendrimer heterogeneity compare defect theoretical treatment theoretical expectations tof ms stoichiometric control size information related signatures related descriptors quantitative validation quantitative information quantitative assessment michael reactions limited number incomplete amidation including trailing h nmr findings highlight experimental descriptors estimated using eda cores divergent approach critical role compact architecture >< sub Low-generation PAMAM dendrimers synthesized via a divergent approach from EDA cores were characterized to assess stoichiometry-dependent structural defects and product heterogeneity. MALDI-TOF MS, RP-HPLC-UV, SEC, and ¹H NMR were employed as complementary techniques to assign and compare defect-related signatures, including trailing-generation species, intramolecular cyclization, and intermolecularly linked dendritic byproducts and/or higher-mass linked dendritic populations. Theoretical molecular weights were estimated using a modified Carothers equation and compared with experimental descriptors, although these comparisons were interpreted as descriptive stoichiometric trends rather than quantitative validation of the theoretical treatment. MALDI-TOF MS revealed repetitive fragment intervals (Δ<i>m/z</i> = 28, 60, 114), consistent with incomplete amidation, cyclization, and retro-Michael reactions. RP-HPLC-UV was used as an orthogonal semi-quantitative chromatographic fingerprinting technique to compare sample heterogeneity under identical analytical conditions. SEC provided apparent hydrodynamic-size information, and SEC-derived molecular-weight-related descriptors were interpreted cautiously due to the compact architecture of dendrimers and calibration with linear polymer standards, while ¹H NMR gave semi-quantitative information on branched and bridged amide environments. The fraction of non-bridged species (<i>f</i>₀) showed a trend consistent with theoretical expectations, although the limited number of stoichiometric conditions precludes rigorous statistical validation. These findings highlight the critical role of stoichiometric control in minimizing defects and reducing structural heterogeneity in low-generation PAMAM products, and emphasize the value of complementary analytical techniques for semi-quantitative assessment of dendrimer heterogeneity. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acsomega.6c08154.s001 https://figshare.com/articles/journal_contribution/Stoichiometry-Dependent_Structural_Defects_in_Low-Generation_PAMAM_Dendrimers/34033317 CC BY-NC 4.0