Low Polymerization Research Articles

Tunable Fe/N co-doped 3D porous graphene with high density Fe-Nx sites as the efficient bifunctional oxygen electrocatalyst for Zn-air batteries

Nitrogen-doped transition metal materials display promising potential as bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Fe/N co-doped three-dimensional (3D) porous graphene (FeN-3D-PG) is prepared via a template method using sodium alginate as the carbon source and low polymerization degree melamine resin as the nitrogen source. The low polymerization degree melamine resin can form complexes with Fe3+ in the aqueous solution and further forms high density Fe-Nx active sites during pyrolysis. Meanwhile, the formed 3D porous structure efficiently promotes the uniform distribution of Fe-Nx active sites. The FeN-3D-PG catalyst exhibits pH-independent ORR activity. For OER, the catalyst possesses a low over potential (370 mV at 10 mA cm−2) in alkaline electrolyte. The Zn-air batteries (ZABs) using FeN-3D-PG as cathode exhibits a power density up to 212 mW cm−2, a high specific capacity of 651 mAh g−1, and the charge-discharge stability of 80 h. This work provides new sight to transition metal materials based ZABs with excellent performance.

Insights on the Atmospheric-Pressure Plasma-Induced Free-Radical Polymerization of Allyl Ether Cyclic Carbonate Liquid Layers.

Plasma-induced free-radical polymerizations rely on the formation of radical species to initiate polymerization, leading to some extent of monomer fragmentation. In this work, the plasma-induced polymerization of an allyl ether-substituted six-membered cyclic carbonate (A6CC) is demonstrated and emphasizes the retention of the cyclic carbonate moieties. Taking advantage of the low polymerization tendency of allyl monomers, the characterization of the oligomeric species is studied to obtain insights into the effect of plasma exposure on inducing free-radical polymerization. In less than 5 min of plasma exposure, a monomer conversion close to 90% is obtained. The molecular analysis of the oligomers by gel permeation chromatography coupled with high-resolution mass spectrometry (GPC-HRMS) further confirms the high preservation of the cyclic structure and, based on the detected end groups, points to hydrogen abstraction as the main contributor to the initiation and termination of polymer chain growth. These results demonstrate that the elaboration of surfaces functionalized with cyclic carbonates could be readily elaborated by atmospheric-pressure plasmas, for instance, by copolymerization.

Extension of the potential intervals of high redox activity and electronic conductivity of polypyrrole films on electrode surface via their electrochemical multi-cycle treatment in monomer-free solution

Thin polypyrrole films (thickness: about 30 nm) have been deposited at electrode surface via potentiostatic oxidation of dilute (1 mM) pyrrole solution in acetonitrile (AN). It has been shown that their subsequent treatment by means of multi-cycle voltammetry within a broad potential range (up to -2.0 V vs. Ag/Ag+ in AN) leads to their "activation", i.e. to a very strong extension of their redox response region in the negative direction as well as to almost uniform distribution of the redox activity within this potential range. Region of their high conductivity under in situ conditions has also extended significantly. Spectral and electrocatalytic properties of such PPy films before and after their "activation" have been analyzed. Two parameters for characterization of the variation of film's properties in the course of its "activation" (redox efficiency of polymerization and width of electroactivity region) have been proposed. Comparison of films deposited at different potentials (from 0.6 V to 0.8 V) has revealed that the effect of their "activation" increases for lower polymerization potential. Films deposited at 0.6 V possess after their "activation" a very broad electroactivity range (almost 2.5 V) and a record high redox charge per monomer unit (its oxidation degree) inside the film in contact with AN solution, 0.45. Such unusual properties of "activated" PPy films make them prospective materials for various applications.

In Search of Effective Anticancer Agents-Novel Sugar Esters Based on Polyhydroxyalkanoate Monomers.

Cancer is one of the deadliest illness globally. Searching for new solutions in cancer treatments is essential because commonly used mixed, targeted and personalized therapies are sometimes not sufficient or are too expensive for common patients. Sugar fatty acid esters (SFAEs) are already well-known as promising candidates for an alternative medical tool. The manuscript brings the reader closer to methods of obtaining various SFAEs using combined biological, chemical and enzymatic methods. It presents how modification of SFAE’s hydrophobic chains can influence their cytotoxicity against human skin melanoma and prostate cancer cell lines. The compound’s cytotoxicity was determined by an MTT assay, which followed an assessment of SFAEs’ potential metastatic properties in concentrations below IC50 values. Despite relatively high IC50 values (63.3–1737.6 μM) of the newly synthesized SFAE, they can compete with other sugar esters already described in the literature. The chosen bioactives caused low polymerization of microtubules and the depolymerization of actin filaments in nontoxic levels, which suggest an apoptotic rather than metastatic process. Altogether, cancer cells showed no propensity for metastasis after treating them with SFAE. They confirmed that lactose-based compounds seem the most promising surfactants among tested sugar esters. This manuscript creates a benchmark for creation of novel anticancer agents based on 3-hydroxylated fatty acids of bacterial origin.

Effect of photo-polymerization mode on the degree of conversion of resin cement under different ceramic materials.

BACKGROUND This study evaluated the effect of different polymerization modes and duration on the degree of conversion (DC) of resin cement under different types of ceramics. METHODS Ceramic materials were divided into 3 groups (n=60): Group 1; CERASMART, Group 2; Vita Enamic and Group 3; Vita MARK II. Each group was then divided into three subgroups (n=20) according to the polymerization mode (A; low-intensity, B; high-intensity, and C; soft-start). Subgroups were then divided into two further groups according to the polymerization time (I; 10 s and II; 20 s). DC of light-cured resin cement beneath different kinds of ceramics was tested using FTIR spectroscopy. Results were compared to a control group cured without overlying ceramic. RESULTS While the type of ceramic and mode of polymerization showed a significant effect on the DC of resin cement, polymerization duration did not. Vita Mark II group showed significantly the highest DC of resin cement, followed by Vita Enamic and Cerasmart. High and low intensity polymerization modes did not show significant difference but both showed significantly lower DC when compared to soft start mode. CONCLUSIONS Type of ceramic and polymerization mode showed a direct effect on the DC of resin cement.

Assessment of polymerization shrinkage of different bulk-fill resin composites

Objectives: This research was designed to evaluate the effect of polymerization shrinkage of different bulk-fill resin composites. Materials & Methods: Ninety extracted molars were prepared as specimens by having a box shape proximal cavity for the restoration of composite resins. The specimens were divided into three main groups (n=30), according to the resin composite materials used (sonic fill, flowable and packable bulk-fill). Profile projector was used for assessment of polymerization shrinkage Results: There is no significant difference between the variables. Sonic fill composite resin has lower polymerization shrinkage than flowable bulk-fill composite and packable bulk-fill composite. The marginal adaptation of sonically activated resin composite is more than the polymerization shrinkage of sonically activated resin composite, while the storage time of sonically activated resin composite is less in bulk-fill .Conclusions: Success of resin composites depends primarily on the degree of polymerization shrinkage as when the shrinkage decrease mostly the post-operative problems decrease.

Fabrication and characterization of low-shrinkage dental composites containing montmorillonite nanoclay.

Dental composites are aesthetic materials widely used in Dentistry for replacing hard dental tissues lost due to caries or traumas. The aim of this study was to fabricate low-shrinkage dental composite charged with nanoclay fillers (montmorillonite Cloisite®-MMT) and evaluate their cytotoxicity and physicomechanical properties. Four dental composites were produced from the same organic matrix: Bis-GMA/TEGDMA (30wt.%). The filler system was constituted of BaSi, SiO2, and MMT in the following concentrations (wt.%): 93.8/6.2/0, 89.1/5.9/5, 86.7/5.8/7.5, and 84.4/5.6/10 (E0: 0; E5: 5%; E7.5: 7.5%; E10: 10% of MMT nanoclays). The following properties were tested: in vitro cytotoxicity, flexural strength, elastic modulus, volumetric shrinkage, water sorption, water solubility, and hygroscopic expansion. Scanning electron microscopy was used to characterize composites' topography. Data were analyzed by one-way ANOVA and Tukey's HSD post hoc test (p < 0.05). MMT nanoclays did not affect the cytotoxicity. E5 and E7.5 groups showed a significant decrease in polymerization shrinkage while maintained the overall physicomechanical properties. The inclusion of 5 and 7.5wt.% of MMT nanoclays allowed the fabrication of dental composites with low cytotoxicity and low polymerization shrinkage, without jeopardizing the overall behaviour of their physicomechanical properties (flexural strength, elastic modulus, water sorption, water solubility, and hygroscopic expansion). These aspects suggest that the usage of MMT nanoclays could be an effective strategy to formulate new dental composites with clinical applicability.

TEKNIK RESTORASI RESIN KOMPOSIT BULK FILL MENGGANTIKAN TEKNIK INKREMENTAL

Introduction. Shrinkage during the polymerization process is the main disadvantage of using composite resins because it creates pressure between the tooth and the restoration which causes failure of the adhesion of the composite resin to the tooth, micro-fissures, and cuspid deflection. Review. To reduce shrinkage that occurs, it is known that conventional composite resins must be inserted into the cavity incrementally or in layers with a maximum thickness of 2 mm per layer. However, the incremental insertion method has several disadvantages, namely that it requires a longer clinical time for restoration. To overcome the shortcomings of these conventional composites, Bulk-fill composite resin was introduced. Composite bulk fill is a sophisticated technology that allows composites to be directly placed on the restoration, has a low polymerization shrinkage to reduce micro-leakage, reduces stress in the presence of elasticity, increases the depth of at least 4 mm translucent at the time of application, is very conducive to light transmission, is more flowable to allow adaptation to the cavity, including cervical margins, it is easy to apply with minimal handling and is resistant to large stresses. Conclusion. With the characteristics possessed by the Bulk-fill composite resin, it is known that the bulk-fill technique in addition to reducing the clinical application time, can also improve the edge adaptation between the restoration and the tooth compared to the incremental technique, without reducing its physical strength

Highly polymerized linear polyimide /H3PW12O40 photocatalyst with full visible light region absorption

The degree of polymerization in polyimides has significant effects on their photoelectric properties. Increase the degree of polymerization in polyimide can improve its light absorption capability as well as reduce the recombination rate of photogenerated electrons and holes. However, it is difficult to promote the polymerization of polyimides by conventional approaches, such as increasing the polymerization temperature since polyimides are susceptible to high temperature and can be decomposed. In this paper, a suitable proportion of phosphotungstic acid was introduced to increase the degree of polymerization of polyimide at a lower polymerization temperature, so as to improve the light absorption capability of the composite and inhibit the recombination of electron and hole. The p-phenylenediamine based polyimide with the one-dimensional linear polymer chain has excellent charge transfer ability, so the POM-π effect formed with phosphotungstic acid is stronger, correspondingly, the light absorption capacity of the composite photocatalyst formed is stronger than that of the cross-linked polyimide/phosphotungstic acid.

Highly Polymerized Wine-Red Carbon Nitride to Enhance Photoelectrochemical Water Splitting Performance of Hematite

Polymeric carbon nitride photocatalyst has attracted much attention due to its visible light response and high chemical stability. However, bulk carbon nitride has a wide band gap and low polymerization, limiting its photocatalytic performance for water splitting. Synthesizing highly polymerized carbon nitride with a narrow band gap still remains challenging. Herein, we propose an ionothermal protocol using supramolecular precursors to fabricate highly polymerized wine-red carbon nitride (WRCN) nanosheets. Both theoretical and experimental investigations revealed that the supramolecular precursor with a high C:N ratio leads to an upward shift of the valence band edge, while the ionothermal synthesis promotes a high polymerization degree, leading to a narrow band gap of 1.82 eV for WRCN. Benefiting from enhanced light absorption and charge separation efficiency, WRCN-loaded hematite photoanode exhibits a much higher photocurrent density than both pristine hematite and bulk carbon nitride decorated hematite. This work may provide a novel strategy to manipulate the electronic structures of carbon nitrides for enhanced photoelectrochemical performances.

Strategies for improving the performance of diallyl bisphenol A-based benzoxazine resin: Chemical modification via acetylene and physical blending with bismaleimide

The benzoxazine resin (DBA-a) synthesized from raw materials of 2,2′-diallyl bisphenol A (DBA), aniline and paraformaldehyde has been well-commercialized, but a reduction in its polymerization temperature and improved comprehensive properties are highly challenging to satisfy the requirements of various composites. Here, we have developed three strategies for improving the performance of DBA-a resin: the first is the chemical modification, synthesizing a novel DBA-based bisbenzoxazine containing acetylene functionality (DBA-ac); the second is the physical blend of bismaleimide (DDM-BMI) and DBA-a, forming a homogenous copolymer; and the third is combining both chemical and physical methods, achieving the DBA-ac/DDM-BMI blend as a new precursor for high-performance thermosets. The newly obtained DBA-ac possesses the advantages of relatively lower polymerization temperature and good thermal stability during the polymerization process. In addition, the polymerization temperature of DBA-ac can be further lowered by blending with DDM-BMI via multiple polymerization mechanisms. Specifically, the resulting copolymeric thermoset derived from DBA-ac/DDM-BMI blend is found to show fascinating properties such as exceptionally low coefficient of thermal expansion (CTE of 37.1 ppm/oC), high thermal stability (Tg of 370 °C), outstanding flame retardancy (THR of 17.6 KJg−1), and low dielectric constant (2.86 at 1 MHz). The current study delivers readily approaches to enhance the performance of thermosetting resins via both chemical modification and physical blending.

3D printing of ultra-tough, self-healing transparent conductive elastomeric sensors

Ultra-tough transparent conductive elastomers (TCEs) with self-healing performance are of great significance for research in the fields of soft robotics, optical display electronics, wearable electronic equipment and human–computer interaction. However, their limitation, such as the desolventizing process, low polymerization rate or balance between toughness and self-healing performance, cause difficulty in manufacturing by the 3D printing technique. Here, we propose a novel preparation strategy for 3D printed TCEs based on the photopolymerization of maleic acid (MA)/choline chloride (ChCl) and acrylamide (AAm)/choline chloride type polymerizable deep eutectic solvents (PDESs). PDES can polymerize into a tough and rich in hydrogen bonds poly(PDES) in a few seconds without solvent evaporation. The printed TCEs with precision of 10 µm have high transparency (95.6%) and stable electrical signals at 50% compression for 10,000 cycles. In addition, efficient self-healing performance due to the dynamic hydrogen bonds of poly(PDES) provides broad application prospects for 3D printed TCEs in long-term pressure-resistant intelligent applications.

Removal of cadmium and tetracycline by lignin hydrogels loaded with nano-FeS: Nanoparticle size control and content calculation

Cadmium (Cd) and tetracycline (TC) cause serious environmental risks. Nanomaterials have been extensively applied for environmental remediation. The size and content of nanoparticles directly affect the removal of contaminants. However, size regulation and quantitative determination of nanoparticles cannot be easily realized. In this study, hydrogels with different polymerization degrees were prepared by adjusting the contents of acrylamide (AM) and sodium lignosulfonate polymeric monomers. Ferrous sulfide (FeS) nanoparticles of different sizes were synthesized in situ within the hydrogels. The nanoparticle size decreased from 600 to 200 nm with increasing hydrogel polymerization degree, and an incomplete crystalline state was observed at the highest polymerization degree. By combining energy dispersive spectroscopy (EDS) images with the maximum between-class variance (Otsu) method, the content of nanoparticles was calculated to be 7.81%, 15.05%, 22.62%, 27.10%, 21.97%, and 23.95%. The distribution state of FeS compounds was also obtained. A low polymerization degree resulted in high FeS dispersal, and a high polymerization degree affected the uniformity distribution based on irregular ion diffusion. The obtained nanocomposites with different polymerization degrees were applied to the removal of Cd and TC in water. The removal capacity for both contaminants revealed a trend of initially increasing and then decreasing. The initial increase was related to the increasing content and decreasing size of the FeS nanoparticles, while the following decrease was due to the decreasing content and incomplete crystallization of the FeS nanoparticles. Overall, changing the proportion of polymeric monomers is an effective way to regulate particle size, and the Otsu method combined with EDS mapping images is a feasible method for calculating the content of nanoparticles.

EFEITO DO ACABAMENTO E POLIMENTO SOBRE A TOPOGRAFIA SUPERFICIAL DE UMA RESINA COMPOSTA CONVENCIONAL E UMA BULK FILL

Introdução: Os compostos resinosos são materiais bastante presentes no dia a dia da clínica odontológica. Apesar de suas vantagens e ótimas propriedades, as resinas compostas convencionais ainda apresentam limitações, como o maior tempo clínico e falhas na adesão. Dessa forma tem-se o surgimento das resinas Bulk-Fill que entre as suas vantagens e propriedades temos: menor tempo clínico, baixa contração de polimerização, maior translucidez, além de propriedades que levam a sua melhor manipulação, tempo clínico e topografia superficial. Objetivo: Avaliar a topografia superficial de restaurações realizadas com diferentes tipos de resina composta antes e após submetê-las a diferentes sistemas de acabamento e polimento. Metodologia: Foram confeccionados 100 corpos de prova (CP), sendo 50 de cada composto resinoso, apresentando cinco grupos (n=10) sorteados de forma aleatória, de acordo com o sistema de acabamento e polimento (AP) empregado. Foram utilizadas as resinas Filtek Z350 XT (3M ESPE, St. Paul, MN, EUA) e a Bulk Fill Filtek One Bulk Fill (3M ESPE, St. Paul, MN, EUA) e os sistemas de acabamento e polimento: Discos de Lixa Sof-Lex Pop On Kit (DL); Discos Diamantado Espiral Sof-Lex (DE); Ponta Enhance (PE) e Broca Carbide Multilaminada nº 0283F (BM), que foram comparados com superfície deixada pela Tira de Poliester (Controle Negativo – CN). Após 7 dias de armazenamento em água destilada, os CP foram submetidos a análise da superfície por meio do Microscópio Eletrônico de Varredura (MEV). Resultados: Os CP da resina Bulk Fill tiveram como melhor resultado o sistema de AP com BM e resultado não satisfatório com DE, enquanto o PE e DL tiveram resultados semelhantes. Os CP da resina Filtek Z350 XT tiveram melhor aspecto visual de lisura superficial no grupo CN e pior resultado no grupo com DE. Conclusões: Dessa forma, o sistema que apresentou melhor resultado foi com a BM na resina Bulk Fill, enquanto a Filtek Z350 XT apresentou-se melhor no grupo C. Porém, ainda são necessários mais estudos que possam levar em considerações outras variações na metodologia empregada para se chegar em um protocolo de acabamento e polimento mais eficiente.

Enhancement of Polymer Structural Ordering in Polymer-Stabilised Blue Phases for Improved Electro-Optical Properties

Polymer-stabilised blue phase (PSBP) could be employed in novel fast response optical and photonic devices. It is inferred that inside PSBPs, the polymers are selectively aggregated by location in −1/2 disclinations, which are defects coexisting with the blue phase as a periodic lattice, thereby extending the temperature range of the blue phase. The polymer aggregate structure in PSBPs strongly affects their physical properties. In this study, we employed a non-destructive synchrotron ultra-small-angle X-ray diffraction analysis to investigate the effect of polymerisation rates on the polymer aggregate structure in PSBPs prepared with monomers of different polymerisation rates and examined the structure formation process of the polymer during polymerisation. When methacrylate monomers, which exhibit a relatively low polymerisation rate, were used to form polymers in PSBP, the resulting polymer was more selectively aggregated at disclinations in the PSBP. Furthermore, the electro-optical effect in the PSBP was successfully improved by reducing the polymer concentration in the PSBPs prepared with the optimised monomer combinations.

Low temperature plasma polymerization: An effective process to enhance the basalt fibre/matrix interfacial adhesion

The interface of fibre reinforced composite materials is deeply affected by the type of sizing applied to the surface of the fibres. In this study, a polymer film based on pure tetravinylsilane (TVS) or its mixture with two different oxygen amounts was deposited on the surface of unsized basalt fibres by plasma enhanced chemical vapor deposition. At first, the influence of the plasma process was investigated through a single fibre tensile test characterization, which did not show any strength degradation of the modified fibres. Subsequently, single fibre pull-out tests were performed to study interfacial strength with an epoxy matrix. The presence of oxygen within the polymer film mixture allowed to increase the interfacial shear strength (IFSS) by 79% compared to untreated basalt fibres, highlighting an excellent fibre/matrix interface for the micro composite. After the interfacial adhesion tests, scanning electron microscopy confirmed the strong bond between the fibre surface and the deposited silane sizing.

Low Power, Low Temperature and Atmospheric Pressure Plasma-Induced Polymerization: Facile Synthesis and Crystal Regulation of Covalent Organic Frameworks.

Low temperature and atmospheric pressure plasma-induced polymerization was demonstrated as a fast and facile strategy for tailoring of packing phase of COF-1 as well as preparing diverse covalent organic frameworks (COFs) including both two-dimensional (2D) COFs and three-dimensional (3D) COFs. By regulating the solvents, the fast construction of well-ordered AB staggered COF-1 and AA eclipsed COF-1 was facilely realized in minutes. The plasma approach presented here led to the rapid preparation of eight classical 2D COFs, including boronate ester-linkage (COF-5, COF-8 and COF-10), azine-linkage (NUS-2), β-ketoenamine-linkage (TpPa, TPBD), imine-linkage (ILCOF-1, Py-COF), and 3D-COF-102 (boroxine linkage) in less than 1 hour. Different from conventional methods, the proposed methodology required much less time, lower power, no extra heating, inert-gas protection and pressure. The fast nucleation and growth of COFs with good crystallinity, morphology and thermal stability can be achieved under mild conditions.

Effect of Na- and Organo-Modified Montmorillonite/Essential Oil Nanohybrids on the Kinetics of the In Situ Radical Polymerization of Styrene.

The great concern about the use of hazardous additives in food packaging materials has shown the way to new bio-based materials, such as nanoclays incorporating bioactive essential oils (EO). One of the still unresolved issues is the proper incorporation of these materials into a polymeric matrix. The in situ polymerization seems to be a promising technique, not requiring high temperatures or toxic solvents. Therefore, in this study, the bulk radical polymerization of styrene was investigated in the presence of sodium montmorillonite (NaMMT) and organo-modified montmorillonite (orgMMT) including thyme (TO), oregano (OO), and basil (BO) essential oil. It was found that the hydroxyl groups present in the main ingredients of TO and OO may participate in side retardation reactions leading to lower polymerization rates (measured gravimetrically by the variation of monomer conversion with time) accompanied by higher polymer average molecular weight (measured via GPC). The use of BO did not seem to affect significantly the polymerization kinetics and polymer MWD. These results were verified from independent experiments using model compounds, thymol, carvacrol and estragol instead of the clays. Partially intercalated structures were revealed from XRD scans. The glass transition temperature (from DSC) and the thermal stability (from TGA) of the nanocomposites formed were slightly increased from 95 to 98 °C and from 435 to 445 °C, respectively. Finally, better dispersion was observed when orgMMT was added instead of NaMMT.

Glycerol polymerization degree effect on the emulsifying properties of polyglycerol esters

AbstractPolymeric emulsifiers based on glycerol and oleic acid were developed and their properties evaluated in palm oil and water solutions. Developed polymeric emulsifiers were polyglycerol‐esters. Polymerization degree of polyglycerol‐esters at different dosages (from 0.2 to 3% w/v) had a significant effect over emulsion stability, water surface tension, droplet size, and viscosity. Polyglycerol‐ester with highest polymerization degree behaved more efficiently as emulsifier. A dosage of 0.5% w/v was required to maintain emulsion stability for a half‐life period of 872 min (~14.5 h); which, is 5.6 and 3.6‐fold longer stability than with the other two polyglycerol‐esters developed. When dosage increased to 3% w/v, the emulsion stability also increased to 3792 min (~2.6 days). Nevertheless, surfactants with lower polymerization degree and molecular weight did not behave the same way. Emulsifier with highest polymerization degree reduced water surface tension by 70% and the mean particle diameter decreased when emulsifier polymerization degree increased. For the viscosity parameter, there were two interesting regions: for shear rates up to 1 s−1 the emulsion behaved as Non‐Newtonian fluid type Shear‐thinning; while, higher shear rates, the viscosity exhibited a Newtonian profile.

Comparative study of free-volume changes in light-cured (dimeth)acrylate-type dental resin composites affected to artificial aging in dry-air and water-immersed mode

This research is intended to compare degradation processes in light-cured (dimeth)acrylate-type polymer/filler dental composites affected to aging in dry-air and water-immersed mode. The positron annihilation lifetime (PAL) spectroscopy has been employed to study changes in atomic-deficient structure in these composites under aging. Under light-curing polymerization initiating crosslinking of monomer chains, fragmentation of free-volume holes in resin matrix dominates over enhanced fraction of trapped positrons, since filler–particles assemblies get to be more tightly covered by surrounding polymer causing disappearing of interfacial voids at the filler–polymer surface. Therefore, the PAL spectra-transforming trend in light-cured composites obeys inverse positron-to-Ps trapping conversion. In contrast, the PAL spectra-transforming trend in these restoratives under aging obeys direct Ps-to-positron trapping conversion. After dry-air aging, the observed changes in the density of annihilation sites are ascribed to a strong agglomeration of Ps-decay holes in polymer sub-system accompanied by weaker agglomeration and appearance of positron traps in filler–polymer sub-system. Under the water aging, the agglomeration of Ps-decaying holes in the polymer sub-system is suppressed due to absorbed water molecules, this effect being slightly revealed at lower polymerization. New positron traps are observed at the filler–polymer interfaces in all light-cured composites. The agglomerated Ps-decay holes in a polymer matrix and positron traps inside filler–particles assemblies and filler–polymer interfaces of artificially aged composites cause their progressive microcracking.