{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,17]],"date-time":"2026-10-17T06:10:57Z","timestamp":1792217457699,"version":"4.4.0"},"reference-count":37,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2022,10,29]],"date-time":"2022-10-29T00:00:00Z","timestamp":1667001600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Among the multitude of polymers with carbon-based macromolecular architectures that easily ignite in certain applications where short circuits may occur, polyimide has evolved as a class of polymers with high thermal stability while exhibiting intrinsic flame retardancy at elevated temperatures via a char-forming mechanism. However, high amounts of aromatic rings in the macromolecular backbone are required for these results, which may affect other properties such as film-forming capacity or mechanical properties; thus, much work has been done to structurally derivatize or make hybrid polyimide systems. In this respect, flexible polyimide films (PI(1\u20134)) containing bulky 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) units have been developed starting from commercial dianhydrides and an aromatic diamine containing two side chain bulky DOPO groups. The chemical structure of PI(1\u20134)) was characterized by 1H NMR, 13C NMR and 31P NMR spectroscopy. The optical properties, including absorption and luminescence spectra of these polymers, were analyzed. All polyimides containing DOPO derivatives emitted blue light with an emission maxima in the range of 340\u2013445 nm, in solvents such as N,N-dimethylformamide, N-methyl-2-pyrrolidone, chloroform, and N,N-dimethylacetamide, while green light emission (\u03bbem = 487 nm for PI-4) was evidenced in a thin-film state. The thermal decomposition mechanism and flame-retardant behavior of the resulting materials were investigated by pyrolysis-gas-chromatography spectrometry (Py-GC), scanning electron microscopy (SEM), EDX maps and FTIR spectroscopy. The residues resulting from the TGA experiments were examined by SEM microscopy images and FTIR spectra to understand the pyrolysis mechanism.<\/jats:p>","DOI":"10.3390\/ijms232113174","type":"journal-article","created":{"date-parts":[[2022,10,30]],"date-time":"2022-10-30T07:26:50Z","timestamp":1667114810000},"page":"13174","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Optical and Flame-Retardant Properties of a Series of Polyimides Containing Side Chained Bulky Phosphaphenanthrene Units"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9432-5479","authenticated-orcid":false,"given":"Mihaela","family":"Homocianu","sequence":"first","affiliation":[{"name":"\u201cPetru Poni\u201d Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda, 41A, 700487 Iasi, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8544-5671","authenticated-orcid":false,"given":"Diana","family":"Serbezeanu","sequence":"additional","affiliation":[{"name":"\u201cPetru Poni\u201d Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda, 41A, 700487 Iasi, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4541-7446","authenticated-orcid":false,"given":"Gabriela","family":"Lisa","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering, Faculty of Chemical Engineering and Environmental Protection, Gheorghe Asachi Technical University of Iasi, Bd. Mangeron 73, 700050 Iasi, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2246-0510","authenticated-orcid":false,"given":"Mihai","family":"Brebu","sequence":"additional","affiliation":[{"name":"\u201cPetru Poni\u201d Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda, 41A, 700487 Iasi, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9017-9926","authenticated-orcid":false,"given":"T\u0103chi\u021b\u0103","family":"Vlad-Bubulac","sequence":"additional","affiliation":[{"name":"\u201cPetru Poni\u201d Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda, 41A, 700487 Iasi, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Wu, Z., He, J., Yang, H., and Yang, S. (2022). Progress in Aromatic Polyimide Films for Electronic Applications: Preparation, Structure and Properties. Polymers, 14.","DOI":"10.3390\/polym14061269"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1016\/j.coco.2019.08.011","article-title":"A review on high temperature resistant polyimide films: Heterocyclic structures and nanocomposites","volume":"16","author":"Ma","year":"2019","journal-title":"Compos. Commun."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"9307","DOI":"10.1021\/acs.macromol.1c01422","article-title":"Intrinsically Black Polyimide with Retained Insulation and Thermal Properties: A Black Anthraquinone Derivative Capable of Linear Copolymerization","volume":"54","author":"Zhou","year":"2021","journal-title":"Macromolecules"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Xiao, S., Akinyi, C., Longun, J., and Iroh, J.O. (2022). Polyimide Copolymers and Nanocomposites: A Review of the Synergistic Effects of the Constituents on the Fire-Retardancy Behavior. Energies, 15.","DOI":"10.3390\/en15114014"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1807738","DOI":"10.1002\/adma.201807738","article-title":"Advances in Polyimide-Based Materials for Space Applications","volume":"31","author":"Gouzman","year":"2019","journal-title":"Adv. Mater."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"9582","DOI":"10.1021\/acsomega.1c06933","article-title":"Study on Chemical Graft Structure Modification and Mechanical Properties of Photocured Polyimide","volume":"7","author":"Liu","year":"2022","journal-title":"ACS Omega"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2303","DOI":"10.1002\/(SICI)1097-4628(19961226)62:13<2303::AID-APP15>3.0.CO;2-3","article-title":"Properties of copolyimides prepared from different tetracarboxylic dianhydrides and diamines","volume":"62","author":"Inoue","year":"1996","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"943","DOI":"10.1002\/pol.20210001","article-title":"Recent development of polyimides: Synthesis, processing, and application in gas separation","volume":"59","author":"Xu","year":"2021","journal-title":"J. Polym. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Hasegawa, M., Ichikawa, K., Takahashi, S., and Ishii, J. (2022). Solution-Processable Colorless Polyimides Derived from Hydrogenated Pyromellitic Dianhydride: Strategies to Reduce the Coefficients of Thermal Expansion by Maximizing the Spontaneous Chain Orientation Behavior during Solution Casting. Polymers, 14.","DOI":"10.3390\/polym14061131"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1081","DOI":"10.1016\/j.eurpolymj.2011.02.008","article-title":"Novel DOPO-based flame retardants in high-performance carbon fibre epoxy composites for aviation","volume":"47","author":"Perret","year":"2011","journal-title":"Eur. Polym. J."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"344","DOI":"10.1016\/j.polymdegradstab.2019.06.024","article-title":"High-efficiency flame retardant behavior of bi-DOPO compound with hydroxyl group on epoxy resin","volume":"166","author":"Jin","year":"2019","journal-title":"Polym. Degrad. Stab."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3899","DOI":"10.1016\/j.polymer.2010.05.059","article-title":"Organo-soluble phosphinated polyimides from asymmetric diamines","volume":"51","author":"Lin","year":"2010","journal-title":"Polymer"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"132031","DOI":"10.1016\/j.cej.2021.132031","article-title":"Flame-Retardant multifunctional epoxy resin with high performances","volume":"427","author":"Liu","year":"2022","journal-title":"Chem. Eng. J."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"11918","DOI":"10.1021\/acs.iecr.0c01277","article-title":"Multifunctional Phosphorus-Containing Triazolyl Amine toward Self-Intumescent Flame-Retardant and Mechanically Strong Epoxy Resin with High Transparency","volume":"59","author":"Ai","year":"2020","journal-title":"Ind. Eng. Chem. Res."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1035","DOI":"10.1016\/S0032-3861(00)00413-4","article-title":"Synthesis and luminescent characteristics of novel phosphorus containing light-emitting polymers","volume":"42","author":"Sun","year":"2001","journal-title":"Polymer"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"109553","DOI":"10.1016\/j.compositesb.2021.109553","article-title":"Imide-DOPO derivative endows epoxy resin with excellent flame retardancy and fluorescence without losing glass transition temperature","volume":"230","author":"He","year":"2022","journal-title":"Compos. Part B Eng."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"13510","DOI":"10.1021\/acsomega.8b01364","article-title":"Polyimides Containing Phosphaphenanthrene Skeleton: Gas-Transport Properties and Molecular Dynamics Simulations","volume":"3","author":"Chatterjee","year":"2018","journal-title":"ACS Omega"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"4220","DOI":"10.1039\/C7PY00687J","article-title":"Soluble, optically transparent polyamides with a phosphaphenanthrene skeleton: Synthesis, characterization, gas permeation and molecular dynamics simulations","volume":"8","author":"Bisoi","year":"2017","journal-title":"Polym. Chem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"110065","DOI":"10.1016\/j.polymdegradstab.2022.110065","article-title":"A phosphorus\/silicon-based, hyperbranched polymer for high-performance, fire-safe, transparent epoxy resins","volume":"203","author":"Shi","year":"2022","journal-title":"Polym. Degrad. Stab."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"219","DOI":"10.1016\/j.jaap.2017.02.003","article-title":"Thermal decomposition and flammability of rigid PU foams containing some DOPO derivatives and other phosphorus compounds","volume":"124","author":"Liu","year":"2017","journal-title":"J. Anal. Appl. Pyrolysis"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"2804","DOI":"10.1002\/pen.25512","article-title":"Synthesis of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative grafted polyethylene films for improving the flame retardant and anti-dripping properties","volume":"60","author":"Xie","year":"2020","journal-title":"Polym. Eng. Sci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"8623","DOI":"10.1021\/acssuschemeng.1c02273","article-title":"Biobased Phosphorus Siloxane-Containing Polyurethane Foam with Flame-Retardant and Smoke-Suppressant Performances","volume":"9","author":"Wang","year":"2021","journal-title":"ACS Sustain. Chem. Eng."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"110047","DOI":"10.1016\/j.compositesb.2022.110047","article-title":"Exploring the effects of cardanol-based co-curing agents with different phosphorus structures on the mechanical and flame-retardant properties of bismaleimide resin","volume":"241","author":"Jiang","year":"2022","journal-title":"Compos. Part B Eng."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1773","DOI":"10.1016\/S0032-3861(01)00751-0","article-title":"Synthesis and characterization of new organosoluble polyaspartimides containing phosphorus","volume":"43","author":"Wu","year":"2002","journal-title":"Polymer"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"791","DOI":"10.1002\/app.12292","article-title":"Polyimides possessing bulky phosphorus groups: Synthesis and characterization","volume":"89","author":"Liu","year":"2003","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"5757","DOI":"10.1016\/S0032-3861(02)00473-1","article-title":"Synthesis and properties of new organosoluble aromatic polyamides with cyclic bulky groups containing phosphorus","volume":"43","author":"Liu","year":"2002","journal-title":"Polymer"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"13","DOI":"10.37358\/RC.21.4.8452","article-title":"Study on thermal and flame retardant properties of phosphorus-containing polyimides","volume":"72","author":"Serbezeanu","year":"2021","journal-title":"Rev. Chim."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1002\/pi.6137","article-title":"Fabrication and study of thermal and combustion resistance of DOPO-functionalized polyamide reinforced with organo-modified Mg(OH)2 nanoparticles","volume":"70","author":"Hajibeygi","year":"2021","journal-title":"Polym. Int."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"10031","DOI":"10.1021\/jp020877f","article-title":"Photophysical Studies on the Mono- and Dichromophoric Hemicyanine Dyes II. Solvent Effects and Dynamic Fluorescence Spectra Study in Chloroform and in LB Films","volume":"106","author":"Huang","year":"2002","journal-title":"J. Phys. Chem. B"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"401","DOI":"10.1007\/s10965-007-9123-9","article-title":"Thermal degradation behaviour of aromatic poly(ester\u2013imide) investigated by pyrolysis\u2013GC\/MS","volume":"14","author":"Guo","year":"2007","journal-title":"J. Polym. Res."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"45694","DOI":"10.1002\/app.45694","article-title":"Thermal stability of end-capped and linear sulfonated polyimides, sulfonated polystyrene, and Nafion 117","volume":"135","author":"Gong","year":"2018","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"477","DOI":"10.1023\/A:1011566127251","article-title":"Thermal Degradation Study of Polymerization of Monomeric Reactants (PMR) Polyimides","volume":"64","author":"Xie","year":"2001","journal-title":"J. Therm. Anal. Calorim."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1016\/0008-6223(96)00189-3","article-title":"The mechanism of polyimide pyrolysis in the early stage","volume":"34","author":"Hatori","year":"1996","journal-title":"Carbon"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"8763","DOI":"10.1021\/jp953630+","article-title":"Systematic Comparison of Experimental, Quantum Mechanical, and Molecular Mechanical Bond Lengths for Organic Molecules","volume":"100","author":"Ma","year":"1996","journal-title":"J. Phys. Chem."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.jaap.2012.11.003","article-title":"Phosphorus-containing poly(trimethylene terephthalate) derived from 2-(6-oxido-6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)-1,4-hydroxyethoxy phenylene: Synthesis, thermal degradation, combustion and pyrolysis behavior","volume":"99","author":"Chen","year":"2013","journal-title":"J. Anal. Appl. Pyrolysis"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"254","DOI":"10.1016\/j.jaap.2018.06.015","article-title":"Thermal decomposition of polyimides containing phosphine-oxide units","volume":"134","author":"Butnaru","year":"2018","journal-title":"J. Anal. Appl. Pyrolysis"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"105524","DOI":"10.1016\/j.jaap.2022.105524","article-title":"Thermal degradation and pyrolysis behavior of wholly aromatic phosphorus-containing thermotropic liquid crystal copolyesters","volume":"164","author":"Wei","year":"2022","journal-title":"J. Anal. Appl. Pyrolysis"}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/23\/21\/13174\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:05:43Z","timestamp":1760144743000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/23\/21\/13174"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,10,29]]},"references-count":37,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2022,11]]}},"alternative-id":["ijms232113174"],"URL":"https:\/\/doi.org\/10.3390\/ijms232113174","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,10,29]]}}}