Contents lists available at ScienceDirect Vibrational Spectroscopy journal homepage: www.elsevier.com/locate/vibspec Raman and FT-IR investigation of neutron and fssion-fragment irradiated DAP polymer Luiz Augusto Stuani Pereira⁎, Carlos Alberto Tello Sáenz Departamento de Física Química e Biologia, Universidade Estadual Paulista, UNESP, 19060-900 Presidente Prudente, SP, Brazil ARTICLE INFO Keywords: DAP detector Irradiation Chemical etching Chemical modifcations Nuclear track ABSTRACT The polymer Diallyl Phthalate (DAP), commonly used as solid-state nuclear track detector (SSNTD), has been characterized via optical microscopy and Raman and FT-IR spectroscopies in three distinct processes: i) without irradiation; ii) irradiated by neutrons and induced fssion fragments and iii) as a function of the chemical etching time. The detectors were exposed to fssion fragments from the induced fssion of 235 U and to the neutrons themselves. The optical microscopy provides information about the morphological changes, while the spectro- scopic techniques provide physical and chemical information over the detector molecular structure. The irra- diation and chemical etching induces molecular degradation and cross-linking of the detector chemical structure as observed in the Raman and FT-IR analyses. According to the spectral profle analyses, the strength of the functional groups eOeCOeOe, CH, CH]CH, C]CH, CeOeC, CeCH 3 ,Ce(CH 3 ) 2 ,CeCH3, C]O, eCH 2 e de- crease and additional CO 2 gases and OH groups are produced. Therefore, the characterization process performed in this work is essential to better comprehend the behavior of the DAP molecular structure under irradiation and chemical etching and also to better understand the track formation process which is related to the etching kinetics. 1. Introduction Solid State Nuclear Track Detectors (SSNTDs) are used and in- vestigated in a vast variety of applications in science and technology, especially in the detection of nuclear radiation through particle track formation [1]. SSNTDs, particularly Diallyl Phthalate (DAP) [2–4], are suitable for the detection of heavy ions such as fssion fragments with a detection efciency of about 100% for both perpendicular and random incidence. On the other hand, the interaction of alpha particles, pro- tons, and, fast neutrons with the detector will not produce etchable tracks. DAP detectors are valuable for quantitative analysis of fssion- able materials and neutron dosimetry [2], but they are not so widely used by the scientifc community for geological dating via fssion track detection [5]. The slowing down (stopping power) of a particle in the detector leads to damages at the level of polymeric bonds, forming the latent track [6,7]. However, for track observation under an optical micro- scope, a chemical etching process is necessary, which amplifes the size of the track ranging from nanometers to micrometers. The most fre- quently model used to explain the etching process steps was developed by Fleisher et al. (1975) [8]. According to this model, there are two distinct parameters, V b (bulk etch rate) and V t (track etch rate), that describe the track etching. The bulk etch rate depends on the detector chemical composition and reactant concentration and temperature. V b can be understood as a dissolution parameter. On the other hand, the chemistry of the V t etch rate is not fully understood. Although nuclear tracks have been extensively studied, there still remain questions re- garding the mechanisms of track formation and its detailed structure [9]. The irradiation and chemical etching of polymers may induce sig- nifcant physical and chemical modifcation of the molecular structure of the irradiated material [10]. Moreover, particle irradiation (such as neutrons, beta particles, alpha particles and fssion fragments) of or- ganic polymers can produce specifc damage known as molecular chain breaking, free radical production, consecutive crosslinking and mole- cular degradation or scissioning. The chemical etching damages are more intense along the latent track in the detector. So, the study of the chemical etching behavior on the bulk of the detector without irra- diation as well as on the nuclear track structure by using diferent material characterization techniques is an important aspect. This work aimed to investigate the chemical modifcations of the molecular structure of the DAP detector induced by irradiation with neutrons and fssion fragments and chemical etching. The detector was characterized via optical microscopy and Raman and FT-IR https://doi.org/10.1016/j.vibspec.2019.102971 Received 3 July 2019; Received in revised form 11 September 2019; Accepted 21 September 2019 ⁎ Corresponding author. E-mail address: gutostuani@hotmail.com (L.A. Stuani Pereira). Vibrational Spectroscopy 105 (2019) 102971 Available online 23 September 2019 0924-2031/ © 2019 Elsevier B.V. All rights reserved. T