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Prof. Damir Klepac
Department of Medical Chemistry, Biochemistry and Clinical Chemistry, Faculty of Medicine, University of Rijeka, Croatia;

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Research Keywords & Expertise

0 Polymer Nanocomposites
0 Polymers
0 Nanoparticles for drug delivery
0 Electron spin resonance (ESR)
0 Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry

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Electron spin resonance (ESR)
Polymers

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Journal article
Published: 28 April 2021 in Molecules
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Chitosan and pectin films were enriched with blackcurrant pomace powder (10 and 20% (w/w)), as bio-based material, to minimize food production losses and to increase the functional properties of produced films aimed at food coatings and wrappers. Water vapor permeability of active films increased up to 25%, moisture content for 27% in pectin-based ones, but water solubility was not significantly modified. Mechanical properties (tensile strength, elongation at break and Young’s modulus) were mainly decreased due to the residual insoluble particles present in blackcurrant waste. FTIR analysis showed no significant changes between the film samples. The degradation temperatures, determined by DSC, were reduced by 18 °C for chitosan-based samples and of 32 °C lower for the pectin-based samples with blackcurrant powder, indicating a disturbance in polymer stability. The antioxidant activity of active films was increased up to 30-fold. Lightness and redness of dry films significantly changed depending on the polymer type. Significant color changes, especially in chitosan film formulations, were observed after exposure to different pH buffers. This effect is further explored in formulations that were used as color change indicators for intelligent biopackaging.

ACS Style

Mia Kurek; Nasreddine Benbettaieb; Mario Ščetar; Eliot Chaudy; Maja Repajić; Damir Klepac; Srećko Valić; Frédéric Debeaufort; Kata Galić. Characterization of Food Packaging Films with Blackcurrant Fruit Waste as a Source of Antioxidant and Color Sensing Intelligent Material. Molecules 2021, 26, 2569 .

AMA Style

Mia Kurek, Nasreddine Benbettaieb, Mario Ščetar, Eliot Chaudy, Maja Repajić, Damir Klepac, Srećko Valić, Frédéric Debeaufort, Kata Galić. Characterization of Food Packaging Films with Blackcurrant Fruit Waste as a Source of Antioxidant and Color Sensing Intelligent Material. Molecules. 2021; 26 (9):2569.

Chicago/Turabian Style

Mia Kurek; Nasreddine Benbettaieb; Mario Ščetar; Eliot Chaudy; Maja Repajić; Damir Klepac; Srećko Valić; Frédéric Debeaufort; Kata Galić. 2021. "Characterization of Food Packaging Films with Blackcurrant Fruit Waste as a Source of Antioxidant and Color Sensing Intelligent Material." Molecules 26, no. 9: 2569.

Journal article
Published: 27 March 2021 in Radiation Physics and Chemistry
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Poly(lactic acid) (PLA), compared to other biodegradable polymers, has one of the highest consumption volumes in the world. Due to its specific properties, especially those that make it ecologically acceptable, it has a wide application from food packaging to medical implants. In this work, commercially available 3D printing filament of PLA was used. The objective was to investigate the effects of γ-radiation on structural changes, mechanical and thermal behaviour of the material. The samples were irradiated with total doses of 25 kGy, 50 kGy, 100 kGy and 200 kGy. The experimental techniques used to investigate the structural changes in PLA filaments were electron spin resonance (ESR) and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and universal testing machine were applied in monitoring changes in thermal and mechanical behaviour, respectively. The formation and stability of free radicals were studied by ESR, which confirmed that the radical concentration depends on the applied absorbed dose, while the spectral lineshape appears to be dose independent. The loss of the ESR signal, directly related to the decrease of radical concentration, was monitored as a function of time for all applied absorbed doses. The breaking force and the Young's modulus were determined and compared. Results have shown that both the concentration and decay rate constant of radicals depend on the absorbed dose. Compressive strength test, a new approach in considering the mechanical changes in irradiated PLA indicated a loss of material elasticity and an increase of brittleness by increasing absorbed dose.

ACS Style

Monica Vidotto; Branka Mihaljević; Gordana Žauhar; Elvira Vidović; Nadica Maltar-Strmečki; Damir Klepac; Srećko Valić. Effects of γ-radiation on structure and properties of poly(lactic acid) filaments. Radiation Physics and Chemistry 2021, 184, 109456 .

AMA Style

Monica Vidotto, Branka Mihaljević, Gordana Žauhar, Elvira Vidović, Nadica Maltar-Strmečki, Damir Klepac, Srećko Valić. Effects of γ-radiation on structure and properties of poly(lactic acid) filaments. Radiation Physics and Chemistry. 2021; 184 ():109456.

Chicago/Turabian Style

Monica Vidotto; Branka Mihaljević; Gordana Žauhar; Elvira Vidović; Nadica Maltar-Strmečki; Damir Klepac; Srećko Valić. 2021. "Effects of γ-radiation on structure and properties of poly(lactic acid) filaments." Radiation Physics and Chemistry 184, no. : 109456.

Journals
Published: 05 December 2018 in Journal of Materials Chemistry A
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Polyaniline cryogels supported with poly(vinyl alcohol) represent soft conducting macroporous materials suitable for conversion to aerogels by freeze-drying and, subsequently, to nitrogen-containing carbogels by carbonization.

ACS Style

Patrycja Bober; Jiří Pfleger; Igor A. Pašti; Nemanja Gavrilov; Sergey K. Filippov; Damir Klepac; Miroslava Trchová; Helena Hlídková; Jaroslav Stejskal. Carbogels: carbonized conducting polyaniline/poly(vinyl alcohol) aerogels derived from cryogels for electrochemical capacitors. Journal of Materials Chemistry A 2018, 7, 1785 -1796.

AMA Style

Patrycja Bober, Jiří Pfleger, Igor A. Pašti, Nemanja Gavrilov, Sergey K. Filippov, Damir Klepac, Miroslava Trchová, Helena Hlídková, Jaroslav Stejskal. Carbogels: carbonized conducting polyaniline/poly(vinyl alcohol) aerogels derived from cryogels for electrochemical capacitors. Journal of Materials Chemistry A. 2018; 7 (4):1785-1796.

Chicago/Turabian Style

Patrycja Bober; Jiří Pfleger; Igor A. Pašti; Nemanja Gavrilov; Sergey K. Filippov; Damir Klepac; Miroslava Trchová; Helena Hlídková; Jaroslav Stejskal. 2018. "Carbogels: carbonized conducting polyaniline/poly(vinyl alcohol) aerogels derived from cryogels for electrochemical capacitors." Journal of Materials Chemistry A 7, no. 4: 1785-1796.

Journals
Published: 26 February 2018 in Nanoscale
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The classical “hard corona–soft corona” paradigm is not valid for HPMA-based nanoparticles.

ACS Style

Damir Klepac; Hana Kostková; Svetlana Petrova; Petr Chytil; Tomáš Etrych; Sami Kereïche; Ivan Raška; David A. Weitz; Sergey K. Filippov. Interaction of spin-labeled HPMA-based nanoparticles with human blood plasma proteins – the introduction of protein-corona-free polymer nanomedicine. Nanoscale 2018, 10, 6194 -6204.

AMA Style

Damir Klepac, Hana Kostková, Svetlana Petrova, Petr Chytil, Tomáš Etrych, Sami Kereïche, Ivan Raška, David A. Weitz, Sergey K. Filippov. Interaction of spin-labeled HPMA-based nanoparticles with human blood plasma proteins – the introduction of protein-corona-free polymer nanomedicine. Nanoscale. 2018; 10 (13):6194-6204.

Chicago/Turabian Style

Damir Klepac; Hana Kostková; Svetlana Petrova; Petr Chytil; Tomáš Etrych; Sami Kereïche; Ivan Raška; David A. Weitz; Sergey K. Filippov. 2018. "Interaction of spin-labeled HPMA-based nanoparticles with human blood plasma proteins – the introduction of protein-corona-free polymer nanomedicine." Nanoscale 10, no. 13: 6194-6204.

Article
Published: 27 January 2017 in Journal of Applied Polymer Science
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We studied natural rubber (NR) filled with frequently used organoclay Cloisite 15A using transmission electron microscopy (TEM), cryoporosimetry, and electron spin resonance (ESR) spectroscopy. Quantitative analysis of the TEM micrographs showed a high level of dispersion without the formation of a rigid filler network. The presence of vacuoles was established on the surface of Cloisite 15A; this indicated weak filler–matrix interactions. The mechanism of reinforcement is, therefore, discussed. The volume of vacuoles was found to be proportional to the crosslinking density; this was confirmed with ESR spin-probe method. The shape of the ESR spectra was highly influenced by the presence of vacuoles. In the NR–Cloisite 10A nanocomposites, vacuoles were absent. The strong interactions implied by this result were confirmed by ESR measurements and are discussed further. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44776.

ACS Style

Mirna Petković Didović; Damir Klepac; A. P. Meera; Sabu Thomas; Srećko Valić. Presence of vacuoles in natural rubber-Cloisite 15A nanocomposites. Journal of Applied Polymer Science 2017, 134, 1 .

AMA Style

Mirna Petković Didović, Damir Klepac, A. P. Meera, Sabu Thomas, Srećko Valić. Presence of vacuoles in natural rubber-Cloisite 15A nanocomposites. Journal of Applied Polymer Science. 2017; 134 (20):1.

Chicago/Turabian Style

Mirna Petković Didović; Damir Klepac; A. P. Meera; Sabu Thomas; Srećko Valić. 2017. "Presence of vacuoles in natural rubber-Cloisite 15A nanocomposites." Journal of Applied Polymer Science 134, no. 20: 1.

Research article
Published: 27 July 2016 in Macromolecules
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ACS Style

Svetlana Petrova; Damir Klepac; Rafał Konefał; Sami Kereïche; Lubomír Kováčik; Sergey K. Filippov. Synthesis and Solution Properties of PCL-b-PHPMA Diblock Copolymers Containing Stable Nitroxyl Radicals. Macromolecules 2016, 49, 5407 -5417.

AMA Style

Svetlana Petrova, Damir Klepac, Rafał Konefał, Sami Kereïche, Lubomír Kováčik, Sergey K. Filippov. Synthesis and Solution Properties of PCL-b-PHPMA Diblock Copolymers Containing Stable Nitroxyl Radicals. Macromolecules. 2016; 49 (15):5407-5417.

Chicago/Turabian Style

Svetlana Petrova; Damir Klepac; Rafał Konefał; Sami Kereïche; Lubomír Kováčik; Sergey K. Filippov. 2016. "Synthesis and Solution Properties of PCL-b-PHPMA Diblock Copolymers Containing Stable Nitroxyl Radicals." Macromolecules 49, no. 15: 5407-5417.

Book chapter
Published: 11 March 2016 in Micro- and Nano-structured Interpenetrating Polymer Networks
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Magnetic resonance spectroscopy is a powerful tool for studying polymer structure and dynamics at the molecular level. In this chapter, the application of various solid-state nuclear magnetic resonance (NMR) techniques (low- and high-resolution 1H, 13C, and 29Si CP MAS) and electron spin resonance (ESR) experiments (nitroxyl radicals used as spin probe or spin label, radicals induced by high-energy radiation and copper(II) ions) in studies of structure and dynamics of interpenetrating polymer networks (IPNs) and semi-interpenetrating polymer network (SIPNs) is presented. On the basis of NMR relaxation measurements and ESR spectra, the relationship between structure and motional heterogeneity is discussed.

ACS Style

Srećko Valić; Mladen Andreis; Damir Klepac. Solid-state NMR and ESR Studies of IPNs. Micro- and Nano-structured Interpenetrating Polymer Networks 2016, 283 -317.

AMA Style

Srećko Valić, Mladen Andreis, Damir Klepac. Solid-state NMR and ESR Studies of IPNs. Micro- and Nano-structured Interpenetrating Polymer Networks. 2016; ():283-317.

Chicago/Turabian Style

Srećko Valić; Mladen Andreis; Damir Klepac. 2016. "Solid-state NMR and ESR Studies of IPNs." Micro- and Nano-structured Interpenetrating Polymer Networks , no. : 283-317.

Journal article
Published: 01 April 2014 in Radiation Physics and Chemistry
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ACS Style

Damir Klepac; Mario Scetar; Goran Baranović; Kata Galić; Srećko Valić. Influence of high doses γ-irradiation on oxygen permeability of linear low-density polyethylene and cast polypropylene films. Radiation Physics and Chemistry 2014, 97, 304 -312.

AMA Style

Damir Klepac, Mario Scetar, Goran Baranović, Kata Galić, Srećko Valić. Influence of high doses γ-irradiation on oxygen permeability of linear low-density polyethylene and cast polypropylene films. Radiation Physics and Chemistry. 2014; 97 ():304-312.

Chicago/Turabian Style

Damir Klepac; Mario Scetar; Goran Baranović; Kata Galić; Srećko Valić. 2014. "Influence of high doses γ-irradiation on oxygen permeability of linear low-density polyethylene and cast polypropylene films." Radiation Physics and Chemistry 97, no. : 304-312.

Journal article
Published: 11 November 2013 in Polymer International
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ACS Style

Jacob John; Damir Klepac; Mirna Petković Didović; K. V. S. N. Raju; Anitha Pius; Mladen Andreis; Srećko Valić; Sabu Thomas. Relaxations and chain dynamics of sequential full interpenetrating polymer networks based on natural rubber and poly(methyl methacrylate). Polymer International 2013, 63, 1427 -1438.

AMA Style

Jacob John, Damir Klepac, Mirna Petković Didović, K. V. S. N. Raju, Anitha Pius, Mladen Andreis, Srećko Valić, Sabu Thomas. Relaxations and chain dynamics of sequential full interpenetrating polymer networks based on natural rubber and poly(methyl methacrylate). Polymer International. 2013; 63 (8):1427-1438.

Chicago/Turabian Style

Jacob John; Damir Klepac; Mirna Petković Didović; K. V. S. N. Raju; Anitha Pius; Mladen Andreis; Srećko Valić; Sabu Thomas. 2013. "Relaxations and chain dynamics of sequential full interpenetrating polymer networks based on natural rubber and poly(methyl methacrylate)." Polymer International 63, no. 8: 1427-1438.

Journal article
Published: 30 March 2013 in Polymer Engineering & Science
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Natural rubber (NR) films with the thickness of about 1 mm were prepared by removing the liquid phase from NR latex, which was previously irradiated. The primary radiation dose varied from 0 kGy (for unirradiated NR) to 200 kGy. Dry NR films were uniaxially stretched, and the degree of deformation, defined as λ = l/l0 (l0 and l being the lengths of relaxed and uniaxially deformed sample, respectively), was varied from λ = 1.0 (relaxed state) to λ = 2.7. Samples were then irradiated with secondary dose, which was chosen to be 100 or 200 kGy. NR films were characterized by differential scanning calorimetry and electron spin resonance–spin probe method. In addition, samples were exposed to accelerated thermal aging, and changes in molecular dynamics and structure were obtained. It has been shown that the application of deformation during the cross‐linking leads to the restriction in segmental mobility for the lower secondary dose, whereas for the higher secondary dose, larger values of λ induce an opposite effect originating from the structural changes. Thermally aged samples show higher amount of the gel phase and consequently higher fraction of slow motional chain segments. POLYM. ENG. SCI., 53:2284–2291, 2013. © 2013 Society of Plastics Engineers

ACS Style

Srećko Valić; Jasminka Bonato; Mladen Andreis; Damir Klepac; Mirna Petković Didović. Preparation and dynamic properties of an anisotropic natural rubber film as viewed by electron spin resonance-spin probe method. Polymer Engineering & Science 2013, 53, 2284 -2291.

AMA Style

Srećko Valić, Jasminka Bonato, Mladen Andreis, Damir Klepac, Mirna Petković Didović. Preparation and dynamic properties of an anisotropic natural rubber film as viewed by electron spin resonance-spin probe method. Polymer Engineering & Science. 2013; 53 (11):2284-2291.

Chicago/Turabian Style

Srećko Valić; Jasminka Bonato; Mladen Andreis; Damir Klepac; Mirna Petković Didović. 2013. "Preparation and dynamic properties of an anisotropic natural rubber film as viewed by electron spin resonance-spin probe method." Polymer Engineering & Science 53, no. 11: 2284-2291.

Journal article
Published: 28 August 2012 in Polymer International
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ACS Style

Damir Klepac; Mario Ščetar; Mia Kurek; Peter E. Mallon; Adriaan S. Luyt; Kata Galić; Srećko Valić. Oxygen permeability, electron spin resonance, differential scanning calorimetry and positron annihilation lifetime spectroscopy studies of uniaxially deformed linear low-density polyethylene film. Polymer International 2012, 62, 474 -481.

AMA Style

Damir Klepac, Mario Ščetar, Mia Kurek, Peter E. Mallon, Adriaan S. Luyt, Kata Galić, Srećko Valić. Oxygen permeability, electron spin resonance, differential scanning calorimetry and positron annihilation lifetime spectroscopy studies of uniaxially deformed linear low-density polyethylene film. Polymer International. 2012; 62 (3):474-481.

Chicago/Turabian Style

Damir Klepac; Mario Ščetar; Mia Kurek; Peter E. Mallon; Adriaan S. Luyt; Kata Galić; Srećko Valić. 2012. "Oxygen permeability, electron spin resonance, differential scanning calorimetry and positron annihilation lifetime spectroscopy studies of uniaxially deformed linear low-density polyethylene film." Polymer International 62, no. 3: 474-481.

Book chapter
Published: 19 August 2011 in Handbook of Multiphase Polymer Systems
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ACS Style

Srećko Valić; Mladen Andreis; Damir Klepac. ESR Spectroscopy of Multiphase Polymer Systems. Handbook of Multiphase Polymer Systems 2011, 551 -584.

AMA Style

Srećko Valić, Mladen Andreis, Damir Klepac. ESR Spectroscopy of Multiphase Polymer Systems. Handbook of Multiphase Polymer Systems. 2011; ():551-584.

Chicago/Turabian Style

Srećko Valić; Mladen Andreis; Damir Klepac. 2011. "ESR Spectroscopy of Multiphase Polymer Systems." Handbook of Multiphase Polymer Systems , no. : 551-584.

Journal article
Published: 05 May 2011 in Polymer Bulletin
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In this research, linear low-density polyethylene (PE-LLD), cast polypropylene (PPcast), and bioriented coextruded polypropylene (BOPP) were used as polymeric materials. Permeability, diffusivity, and solubility of N2, O2, and CO2 through above polymers were obtained at different temperatures. The structure and thermal–mechanical features of the films were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The permeability, diffusivity, solubility, and their temperature dependency were studied by correlations with gas molecule properties. The highest permeation coefficients (>3.8 × 10−8 cm3 cm−1 s−1 bar−1) are obtained for PPcast at 60 °C. Activation energy for permeation follows the sequence: N2 > O2 > CO2 for PE-LLD and PPcast. On the other hand, the diffusion activation energy follows the order: O2 > CO2 > N2 and N2 > CO2 > O2 for PE-LLD and PPcast, respectively. In the case of BOPP, activation energy follows the sequence: O2 > CO2 > N2; CO2 > N2 > O2; and O2 > CO2 > N2 for permeation, diffusion, and heat of sorption, respectively.

ACS Style

Mia Kurek; Damir Klepac; Mario Ščetar; Kata Galić; Srećko Valić; Yong Liu; Weimin Yang. Gas barrier and morphology characteristics of linear low-density polyethylene and two different polypropylene films. Polymer Bulletin 2011, 67, 1293 -1309.

AMA Style

Mia Kurek, Damir Klepac, Mario Ščetar, Kata Galić, Srećko Valić, Yong Liu, Weimin Yang. Gas barrier and morphology characteristics of linear low-density polyethylene and two different polypropylene films. Polymer Bulletin. 2011; 67 (7):1293-1309.

Chicago/Turabian Style

Mia Kurek; Damir Klepac; Mario Ščetar; Kata Galić; Srećko Valić; Yong Liu; Weimin Yang. 2011. "Gas barrier and morphology characteristics of linear low-density polyethylene and two different polypropylene films." Polymer Bulletin 67, no. 7: 1293-1309.

Journal article
Published: 01 May 2010 in Polymer
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ACS Style

Jacob John; Damir Klepac; Mirna Petkovic Didovic; C.J. Sandesh; Yong Liu; K.V.S.N. Raju; Anitha Pius; Srećko Valić; Sabu Thomas. Main chain and segmental dynamics of semi interpenetrating polymer networks based on polyisoprene and poly(methyl methacrylate). Polymer 2010, 51, 2390 -2402.

AMA Style

Jacob John, Damir Klepac, Mirna Petkovic Didovic, C.J. Sandesh, Yong Liu, K.V.S.N. Raju, Anitha Pius, Srećko Valić, Sabu Thomas. Main chain and segmental dynamics of semi interpenetrating polymer networks based on polyisoprene and poly(methyl methacrylate). Polymer. 2010; 51 (11):2390-2402.

Chicago/Turabian Style

Jacob John; Damir Klepac; Mirna Petkovic Didovic; C.J. Sandesh; Yong Liu; K.V.S.N. Raju; Anitha Pius; Srećko Valić; Sabu Thomas. 2010. "Main chain and segmental dynamics of semi interpenetrating polymer networks based on polyisoprene and poly(methyl methacrylate)." Polymer 51, no. 11: 2390-2402.

Journal article
Published: 01 June 2008 in Radiation Physics and Chemistry
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ACS Style

I. Dubrović; Damir Klepac; S. Valić; G. Žauhar. Study of natural rubber crosslinked in the state of uniaxial deformation. Radiation Physics and Chemistry 2008, 77, 811 -817.

AMA Style

I. Dubrović, Damir Klepac, S. Valić, G. Žauhar. Study of natural rubber crosslinked in the state of uniaxial deformation. Radiation Physics and Chemistry. 2008; 77 (6):811-817.

Chicago/Turabian Style

I. Dubrović; Damir Klepac; S. Valić; G. Žauhar. 2008. "Study of natural rubber crosslinked in the state of uniaxial deformation." Radiation Physics and Chemistry 77, no. 6: 811-817.

Journal article
Published: 01 May 2008 in Macromolecular Symposia
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ACS Style

Mirna Petkovic Didovic; Damir Klepac; Srećko Valić. ESR - Spin Probe Method in Studying Natural Rubber: an Effect of the Probe Incorporation Temperature. Macromolecular Symposia 2008, 265, 144 -147.

AMA Style

Mirna Petkovic Didovic, Damir Klepac, Srećko Valić. ESR - Spin Probe Method in Studying Natural Rubber: an Effect of the Probe Incorporation Temperature. Macromolecular Symposia. 2008; 265 (1):144-147.

Chicago/Turabian Style

Mirna Petkovic Didovic; Damir Klepac; Srećko Valić. 2008. "ESR - Spin Probe Method in Studying Natural Rubber: an Effect of the Probe Incorporation Temperature." Macromolecular Symposia 265, no. 1: 144-147.