Synthesis of Narrow Polydispersity Block Copolymers of PtBA-PS by Novel RAFT Polymerization Technique

The synthesis of narrow disperse polystyrene (PS) and poly-t-butylacrylate (PtBA) was carried out by copolymerization using benzyldithiobenzoate as the chain transfer agent (CTA). Benzyl dithiobenzoate as a reversible addition-fragmentation chain transfer (RAFT) agent has high transfer coefficient in polymerization of styrene to produce PS with higher molecular weight than that of calculated, in contrary with polymerization of t-butylacrylate to produce PtBA. These results were attributed to instability the benzyl dithiobenzoate as RAFT agent under the reaction conditions. PS as a macro-CTA is not active for t-butylacrylate polymerization due to low transfer coefficient. On the other hand PtBA as the macro-CTA is active to polymerize styrene to produce PtBA-PS block copolymer with high transfer coefficient if PtBA as macro-CTA have narrow polydispersity. The RAFT agent appears to degrade over a period of time when it is left at room temperature, which was evident from the results of PtBA

Synthesis of Narrow Polydispersity Block Copolymers of PtBA-PS by Novel RAFT Polymerization Technique

The synthesis of narrow disperse polystyrene (PS) and poly-t-butylacrylate (PtBA) was carried out by copolymerization using benzyldithiobenzoate as the chain transfer agent (CTA). Benzyl dithiobenzoate as a reversible addition-fragmentation chain transfer (RAFT) agent has high transfer coefficient in polymerization of styrene to produce PS with higher molecular weight than that of calculated, in contrary with polymerization of t-butylacrylate to produce PtBA. These results were attributed to instability the benzyl dithiobenzoate as RAFT agent under the reaction conditions. PS as a macro-CTA is not active for t-butylacrylate polymerization due to low transfer coefficient. On the other hand PtBA as the macro-CTA is active to polymerize styrene to produce PtBA-PS block copolymer with high transfer coefficient if PtBA as macro-CTA have narrow polydispersity. The RAFT agent appears to degrade over a period of time when it is left at room temperature, which was evident from the results of PtBA

Isolasi Nanokristalin Selulosa Bakterial Dari Jus Limbah Kulit Nanas: Optimasi Waktu Hidrolisis

Nanokristalin selulosa (NCC) adalah bionanomaterial yang terbarukan, berkelanjutan, ramah lingkungan, dan potensi penggunaannya sangat luas. Salah satu metode untuk mengisolasi NCC dari selulosa adalah dengan hidrolisis menggunakan asam. Waktu hidrolisis adalah salah satu faktor yang sangat menentukan keberhasilan isolasi NCC disamping konsentrasi asam dan suhu hidrolisis. Penelitian ini difokuskan untuk memperoleh waktu hidrolisis optimum untuk isolasi NCC. Selulosa bakterial (BC), yang disintesis menggunakan media kultur jus limbah kulit nanas, digunakan sebagai sumber selulosa yang murah dan ramah lingkungan. Optimasi waku hidrolisis dikarakterisasi dengan stabilitas dispersi, %-hasil, dan diameter partikel rata-rata yang diukur menggunakan Particle Size Analyzer (PSA). Waktu optimum hidrolisis yang memberikan dispersi stabil dengan %-hasil terbanyak (62%) dan ukuran partikel terkecil (diameter rata-rata 41,6 nm) adalah 25 menit pada suhu dan konsentrasi asam tertentu. Analisis FTIR memperlihatkan spektrum NCC mirip dengan BC-asal dengan puncak-puncak serapan khas untuk selulosa. Sedikit pergeseran terjadi pada puncak sekitar 2900 cm−1 dan 1430 cm−1 yang disebabkan oleh adanya peningkatan derajat kristalinitas, hal ini menunjukkan pula bahwa BC telah berubah menjadi NCC. Pengamatan dengan Transmission Electron Microscopy (TEM) terhadap NCC memperlihatkan morfologi yang berbentuk jarum

Biodegradation of Poly(R,S)-β-hydroxybutyrate and its copolymer with δ-Valerolactone Synthesized by Aluminoxane Catalyst

Poly(R,S)-β-hydroxybutyrate (PHB) and its copolymers with δ-valerolactone were synthesized by ring-opening copolymerization of (R,S)-β-butyrolactone (β-BL) and δ-valerolactone (δ-VL) monomers in the presence of a tetraisobutyldialuminoxane catalyst. The biodegradability of these polymers by using activated sludge was studied in an aerobic medium. The objective of this work was to determine the influence of structure and crystallinity of polymers on their degree of biodegradation and initial degradation rate. It was shown that the degradation rate for bacterial P(R)-HB with 100 % (R) isotactic structure was the highest and the final biodegradation was reached around 94 % after incubation time of 35 days. Whereas the final biodegradation about 88 % was obtained for atactic P(R,S)-β-HB synthesized by using aluminoxane catalyst. The influence of the structure and crystallinity on the initial biodegradation rate were observed for the copolymers in various composition of comonomers. All these copolymers with the PHB ratio more than 10 % exhibit highly degree of biodegradation, about 85 % after 35 days of incubation time

Structure and Properties of Polymers Prepared by Polymerization of 2,2-Dimethyl-1,3-Propandiol and ε-Caprolactone Monomer

Poly(ε-caprolactone) (PCL) is very attractive synthetic polymer due to its properties, such as a high permeability, the lack of toxicity, and also biodegradability. However, it has limited application because of low melting point (60 °C), high crystallinity, and brittleness. The aim of the experiments is designed to improve the properties of PCL by formation of their polymers with 2,2-dimethyl-1,3-propandiol monomers with various chain length as a raw material to prepare poly(urethane-ester). These polymers were synthesized by a ring-opening polymerization of 2,2-dimethyl-1,3-propandiol and ε-caprolactone monomers in various composition in the presence of 1-hydroxy-3-chloro-tetraisobuthyldistanoxane as a catalyst. Polymers were characterized by analysis of functional groups (FTIR), microstructure (1H and 13C NMR), viscosity, hydroxyl number, and also melting point of polymers (DSC). Based on the structure analysis indicate that polymerization of 2,2-dimethyl-1,3-propandiol and ε-caprolactone monomers produced polymers with various molecular weights, which depend on the ratio of ε-caprolactone / 2,2-dimethyl-1,3-propandiol used in polymerization. The reactivity of CL monomer decreases to the active site of polymers with longer chain size. The melting points of polymers increase with the increasing of ε-caprolactone composition used in polymerization, whereas hydroxyl number decreases

Pengembangan Soal Tes Penalaran Tinggi Berbasis Komputer pada Bahasan Trigonometri SMA

This study aims to (1) Developing the higer oreder thinking skills test on computer based in the subject of trigonometric SMA. (2) Knowing the feasibility of a higer oreder thinking skills tests computer based made on the subject of trigonometric SMA. This research is a research and development (Research & Development). The development method used in this study follows a simple development procedure suggested by Borg and Gall consisting of five steps: (1) Product analysis to be developed, (2) initial product development, (3) Expert Validation and product revision, (4) ) Limited field trials and product revisions, (5) Main-scale field trials and end products. The results of this study is a computer-based test entitled: "Computer Based Test Problems On High Trigonometric Discussion" which is packaged in the form of Comapct Disk (CD). The computer-based tests were tested limited trial of 30 students and a major trials of 34 SMA N 10 Yogyakarta. Problem-based computer test has met the validity, reliability, objectivity, praktibilitas, and economical. Validation results show a computer-based test is worth using. This is supported by: average grain matter about 4.80 (very good) and average media expert 4,76 (very good) and student questionnaire score 39,03 (very good. Â Research suggestions, the product should be used by students as an exercise in computer based reasoning.

COPOLYMERS OF 2,2-DIMETHYL-1,3-PROPANDIOL AND &#948

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