ITU ARI Bulletin of Istanbul Technical University

Effects of Synthesized C-S-H on the Hydration and Micromechanical Behaviour of Alite Paste and Cement Paste

Adile Aslı Özbora — 2024-03-07

To explain and quantify the relation between the microstructure of synthesized C-S-H incorporated cement-based materials and their engineering properties, it is crucial to monitor and understand the effects of synthesized C-S-H on the hydration of cementitious materials. In this study, it is aimed at optimizing and tailoring C-S-H formation in alite and cement pastes through the addition of C-S-H seeds for engineering performance and sustainability related properties while modifying the evolution of the microstructure of these pastes. To evaluate the hydration kinetics, isothermal calorimetry test was used to investigate the hydration of alite and cement pastes. Additionally, to investigate the micromechanical performance of alite and cement pastes, compressive strength values of the mixes with different percentages of synthesized C-S-H (0%, 4% and 8% by weight of alite and 0%, 1.25%, 2.5%, 4% and 8% by weight of cement) were determined at different ages on minicubes of 10x10x10mm. The results that were analysed showed that the addition of synthesized C-S-H significantly accelerated the hydration of alite phase and cement. This increase of the degree of hydration of both is ensured by promoting the growth of C-S-H clusters into the pore solution instead of around the tricalcium silicate or cement grains. The extent of the acceleration was dependant on the amount (and chemical composition) of the C-S-H seeds. As the chemical and mechanical properties of C-S-H can be controlled, this method proves that tailoring the nanostructure of the hydration products of alite phase or cement through the addition of synthesized C-S-H is possible for optimum engineering performance and sustainability related properties.

GİRİŞ

Barbaros AKKURT — 2024-02-06

2023 senesi İTÜ’ye iyi gelmedi. Önce Yusuf, arkadan Aral gitti ve her ikisi de İTÜ’nün akademik performansında büyük iki delik bıraktılar. Yusuf benim iyi bir dostum, bazen da dert ortağımdı. Derdimiz ise Türkiye’nin bilim dünyasındaki yeriydi. Yusuf üstün başarılı bir kimyacıydı ve en son konuştuğumuzda ona Nobel getirebilecek projelerini anlatmıştı. Ben de ona eğer Nobel alırsa, İTÜ kampüsünün ortasına çıkıp zevkten göbek atacağımı söylemiştim. Ne yazık ki ölümü buna izin vermedi.

Yusuf’la bilimsel ilgilerimiz birbirlerinden epey farklı olduğu için bir araya geldiğimizde oradan buradan sohbet ederdik, Türkiye’nin bilimdeki geriliğinden de dem vurup üzüntülerimizi paylaşırdık. Ama Yusuf asla kötümser değildi. Müthiş zekâsı ve hazırcevaplığı, nüktedanlığına ayrı bir lezzet katardı. Ben Yusuf’u hiç asık yüzlü görmemiştim. Ama ölümü hepimizin yüzünü astı, en azından ben hâlâ yüzümü eski haline getiremiyorum. Onun esprilerini, hınzır sataşmalarını düşünüyorum gülebilmek için, ama onları yapan ortada olmayınca yüzüm eski haline gelmeyi reddediyor. Şimdi Yusuf’un arkada bıraktıklarına düşen en önemli görev onun başlattığı ivmeyi hızlandırarak sürdürmek ve onun almasını hepimizin çok istediği kimya Nobel ödülünü üniversitemize getirmek.

O zaman da İTÜ belki dünya çapında arzu edilen bir “Yusuf Yağcı Kimya Madalyasını” hayata geçirir, bizden sonraki nesiller Yusuf’un o her zaman gülümseyen, dost yüzünü bir altın yüzeyde görüp heyecanlarına heyecan katabilirler.

Yusuf öldü. Ama onun eserinin, onun azîz hâtırasının ilelebet yaşamasını temin etmek artık arkada bıraktığı bizlerin borcudur. Nur içinde yat azîz arkadaşım. Senin saçtığın ışıklar hepimizin sanki daha da pırıltılı görülmemizi sağlıyor bu çeyrek bin yıllık üniversitemizde. İnan, sen kalbimizde her zaman var olacaksın, anılarınla İTÜ’ye nur yağdırmaya devam edeceksin.

Hyaluronic Acid-Enriched Pectin-Based Hydrogel Films for Wound Healing

Ö. Zeynep Güner Yılmaz — 2024-02-03

Wound healing research is always looking for approaches to improve patient care. Advanced wound dressings are critical in this process. In this context, the article focuses on the comprehensive examination of the potential of hyaluronic acid-enriched pectin-based hydrogel films to advance wound healing. For comparative analysis, two formulations were prepared: a pectin matrix and a film containing fifty percent hyaluronic acid and pectin. Both formulations were cross-linked using calcium ions. The hydrogels underwent thorough characterization, including Fourier-transform infrared spectroscopy analysis for chemical composition, differential scanning calorimetry for thermal properties determination, and scanning electron microscope imaging for morphological examination of cross-sections. We thoroughly examine their fluid-handling capacities, dehydration rates, and water vapor permeability through meticulous inspection. These characteristics have a significant impact on elasticity, moisture retention, and overall effectiveness throughout the healing process. To demonstrate the transformative potential of HA-enriched pectin-based hydrogel films, we compare their properties to those of pectin hydrogel and a commercial alginate-based wound dressing. As a result, the investigation revealed a notable enhancement in the transparency of the wound dressing, a crucial factor for facilitating continuous monitoring of the wound site without necessitating frequent removal of the dressing. The improvement in water vapor permeability suggests an optimized moisture balance, fostering an environment conducive to efficient wound healing. Moreover, the smoother film contributes to the overall comfort for patients and potentially minimizes skin irritation and discomfort during prolonged wear. The innovative features identified in this study collectively point towards the prospect of these hydrogel films not only as effective wound dressings but also as a step forward in addressing the practical aspects of patient comfort and convenience.

Visible Light-Induced Fabrication of a Clickable Cu(I) Benzophenone Dicarboxylate Polymer - Polyacrylamide Hydrogel Composite

Sena Ermiş — 2024-02-03

Hydrogels are a class of hydrophilic polymers that have been widely applied in numerous fields, most of which are related to bioengineering such as tissue scaffolds, biosensing and antibacterial activity. Especially, polyacrylamide (PAAm) hydrogels, due to their superior stability, non-toxicity and viscoelasticity, have been extensively studied over the last two decades in different bio-related applications. Coordination polymers (CPs) including metal-organic frameworks (MOFs), due to tunability of the organic linkers and metal ions, and their robustness, have been incorporated with hydrogels in order to improve the physical/chemical properties of the final composite. Herein, we report for the first time, the use of a photoactive Cu(I) coordination polymer, as Norrish type II photoinitiator, for the visible light-induced in situ fabrication of a clickable and highly-crosslinked Cu(I)CP-PAAm hydrogel composite using water as the solvent. Due to the high stability of the Cu(I)CP in water, that was demonstrated by powder X-ray studies, the release of copper ions was observed to occur after more than two days. Another advantage of the developed synthetic method, is the possibility to readily post-modify the hydrogel-composite by employing an azide-functionalized polymer through internal copper-catalyzed azide-alkyne click reaction.

Perspectives on the Curing of Benzoxazine Resins

Barış Kışkan — 2024-02-24

Benzoxazines are a class of heterocyclic compounds that can be polymerized to form polybenzoxazines, which have excellent properties such as thermal stability, flame retardance, low shrinkage, and chemical resistance. The curing of benzoxazines involves a thermal cationic ring-opening polymerization, which can be influenced by various factors such as catalysts, co-monomers, temperature, and time. In general, the curing temperatures of benzoxazines are considered as high and lie between 180 ⁰C and 260 ⁰C depending on the monomer structure. This nature of benzoxazine resins could limit their wider applications in different areas. Therefore, lowering the curing temperatures could play a critical role in the benzoxazine resin chemistry. This review summarizes the recent advances in the understanding of the curing mechanisms of benzoxazine resins, with a focus on the factors influencing the curing kinetics and the resulting material properties.

Strecker 3-Component Reaction for Post-Polymerization Modification of Pendant Aldehyde Functional Polymers

Mine Aybike Ersin — 2024-02-13

Aldehydes have always been useful building blocks in organic chemistry due to their high and diverse reactivity. They also offer easy access to various other functionalities and allow reactions to be performed under mild conditions. This distinguished versatility has allowed aldehyde-bearing polymers to be a good platform for post-polymerization modification reactions to prepare functional polymers. This study exploited the Strecker 3-component reaction to obtain polymers with α-aminonitrile groups at the side chain for the first time. For this purpose, firstly, an aldehyde-functional polymer was synthesized from 4-formylphenyl methacrylate through free radical polymerization and then modified with amine compounds in the presence of trimethylsilyl cyanide and a catalytic amount of p-toluenesulfonic acid at room temperature. The spectroscopic analyses confirmed the successful synthesis of corresponding α-aminonitriles.

Mechanical Recycling of PET– Current Situation and Perspectives

Yonca Alkan Goksu — 2024-04-01

The exponential rise in global petroleum-based polymer production and consumption presents a significant environmental challenge, with projections indicating an alarming growth in annual plastic waste to 460 million tons by 2030. Despite the widespread use of poly(ethylene terephthalate) (PET) for its economic appeal and versatility, the accumulation of PET waste calls for urgent and effective recycling strategies. The critical importance of PET recycling to reduce environmental impact is emphasized by current worldwide efforts, such as restrictive laws imposed by the EU and the specific material limits implemented in countries like South Korea and Japan. While several mechanisms are employed for PET recycling, mechanical recycling emerges as a standout approach due to its industry applicability. However, challenges arise from PET degradation during reprocessing, necessitating innovative solutions. In this context, diverse chain extenders, including oxazolines, isocyanates, anhydrides, epoxides, and the promising Meldrum's acid derivatives, have been explored. These agents exhibit significant potential in improving the characteristics of PET throughout the recycling process, providing an avenue to reduce the environmental impact of plastic waste. This comprehensive perspective explores the current status and future potential of PET recycling. The combination of global initiatives, mechanical recycling innovations, and advanced chain extender strategies pave the way for a more sustainable and environmentally conscious future in polymer recycling.

Photo-mediated Metal-Free Atom Transfer Radical Polymerization: Mechanistic Insight and Future Perspectives

Mustafa Ciftci — 2024-04-08

Among the various controlled/living radical polymerization approaches, atom transfer radical polymerization (ATRP) stands out as the most commonly employed technique. Nevertheless, the requirement for a metal catalyst poses a disadvantage and constrains its wider applicability. In light of advancements in reducing the concentration of metal catalysts, recent developments have demonstrated that ATRP can be conducted under metal-free conditions through light irradiation. Based on its unique properties, it has become a valuable tool in the design and synthesis of tailorable polymers for a wide range of applications. In this mini-review the fundamental features of the reductive and oxidative quenching mechanism of metal-free ATRP are provided in addition to the potential applications.