RAFT Method Research Articles

Sargassum sp. Growth Cultivated with Different Seed Weights on Floating Raft System in Ekas Bay East Lombok

Sargassum sp. is seaweed from the group of brown algae belonging to the Phaecophyceae class that can be found in Indonesian. Sargassum sp. contains polysaccharides in the form of alginate which can be used as raw materials and additives in the food, drug, and cosmetic industries. The aim of this study was to analyze the growth of Sargassum sp. which are cultivated with different seed weights on the floating rafts. The research was conducted from November 2020 to March 2021 in Ekas Bay, East Lombok, West Nusa Tenggara. The research method used is an experimental method using a completely randomized design (CRD) consisting of five treatments with four replications. The treatments were differences in the weight of the initial seeds used, namely treatment A (25 g), B (50 g), C (100 g), D (150 g), and E (200 g). Sargassum sp. Cultivation was carried out for a month. The results were the highest absolute weight was in treatment E with 550 g and the lowest occurred in A with 262.5 g. The highest specific growth was in treatment A with 8.13%/day and the lowest was in E with 4.4%/day. This study concluded that different seedling weights had a significant effect on the growth of Sargassum sp. cultivated using the floating raft method

Polyvinylidene fluoride as a neat and the synthesized novel membranes based on PVDF/polyvinyl pyrrolidone polymer grafted with TiO2 nanoparticles through RAFT method for water purification

Polyvinylidene fluoride as a neat and the synthesized novel membranes based on PVDF/polyvinyl pyrrolidone polymer grafted with TiO2 nanoparticles through RAFT method for water purification

Business Prospects for Hydroponic Vegetables in the Midst of The COVID-19 Pandemic : A Case Study on “Indah Berbagi Foundation”

The Covid-19 outbreak has occurred and has had a substantial impact on many aspects of public life that are not only a health problem, but also affect the world economy and the environment in various ways. It seems that no country can avoid it and is not affected by its existence, and Indonesia is no exception. The main objective of this study is to determine the economic resilience of the community in dealing with Covid 19 pandemic espesially in hydroponic vegetable business. Data were collected through in-depth interviews with hydroponic activists, documentation and observation conducted during September 2020. The collected data were analyzed through data triangulation. The results show that hydroponic vegetable business developed by Indah Berbagi Foundation has implemented the floating hydroponic method or also known as the Floating Raft method and the Nutrient Film Technique (NFT) system. Hydroponic vegetable business was profitable and the technology used compatible with characteristics of areas that have limited land. During the pandemic, the public demand for hydroponic vegetables increased quite high along with the increasing awareness of the public to consume healthy vegetables to maintain endurance, therefore in addition to providing good nutrition for body resistance during a pandemic. Using payback period method, it’s known that the hydroponic vegetable business can provide benefits and fast return on investment so that it is very useful in supporting the economic resilience of the community

Growth of oyster (Crassostrea sp.) with different stocking density in Alue Naga waters, Banda Aceh Indonesia

Oyster (Crassostrea sp.) is one of the potential bivalves that have big potency to increase Indonesian economic income. This study aimed to investigate the growth of oysters (Crassostrea sp.) with different densities, and to determine the effect of different stocking densities on growth and survival in the submerged raft method in oyster aquaculture in Alue Naga district, Indonesia. A completely randomized design model (CRD) was used with three treatments and triplications. There were three different stocking densities namely 25, 30, and 35 ind/1500 cm2. The results showed that the absolute length and weight of oysters with a density of 25, 30 and 35ind/1500 cm2 were ranged from9.49 mm and 10.60 grams, 4.83 mm and 9.13 grams and 4.62 mm and 5.76 grams respectively. It is concluded that the best growth oyster in this study was at 25 ind / 1500 cm2 stocking densities.

PEMBERDAYAAN PETANI RUMPUT LAUT DI KAMPUNG SARAWANDORI DISTRIK KOSIWO KABUPATEN KEPULAUAN YAPEN

The potential for marine products in the Yapen Islands is very abundant, including seaweed. However, it should be noted that coastal communities who work as seaweed farmers with all their limitations also face several problems, including limited knowledge and skills in seaweed cultivation, use of simple tools (raft method), traditional/hereditary cultivation methods, and the marketing of crops, whose reach is still limited. For this reason, the Regional Government through the Marine and Fisheries Service provides support and assistance in the context of empowering seaweed farmers. The purpose of writing this is to find out the process of empowering seaweed farmers in Sarawandori Village. Else, to explore the obstacles and supporting factors of the empowerment. This research used a qualitative research method with a descriptive approach. The results showed that the empowerment of seaweed farmers had been running even though the results were not optimal. For this reason, the government through the Yapen Islands Regency Maritime Affairs and Fisheries Office seeks to help farmers in the seaweed cultivation process, and facilitate farmers to be able to use more sophisticated technology and expand the marketing reach of seaweed and its processed products from Sarawandori Village to outside the Yapen Islands.
 Keywords: Empowerment, Seaweed, Farmer, Yapen Regency

Coassembly behavior and kinetics of cellulose nanocrystals and pH-responsive diblock copolymers PMMA-b-PDEAEMA at oil/water interfaces and applied on the liquid tubule formation

In this work, a series of oil soluble diblock copolymers poly(methyl methacrylate)-b-poly[2-(dimethylamino)ethyl methacrylate] (PMMAm-b-PDEAEMAn; where m is fixed at 49 and n is varied from 3 to 12) are synthesized using a reversible addition-fragmentation chain transfer RAFT method. The copolymers exhibit pH-dependant interfacial activities and behave as macromolecular surfactants under strong acidic conditions. The coassembly behavior and kinetics of cellulose nanocrystals (CNCs) and the copolymer at the water/toluene interface is probed by tracking the dynamic interfacial tension using pendant drop tensiometry. At low pH such as 2 and 3, the film that CNCs coassemble with the copolymer at the oil/water interface can stabilize the pendant drop from dripping down. At a higher pH value, CNCs enhance the interfacial activity of the copolymer through interfacial tension measured and emulsions test. When investigating the coassembly kinetics, it is found that the interfacial protonation reaction of the copolymer and absorbing at the oil/water interface is the rate-determining step and electrostatic binding with CNCs is a much faster process. Besides, the interfacial activity of PMMAm-b-PDEAEMAn is enhanced as n increases and the interfacial coassembly with CNCs is accelerated. A nanoparticle film can be formed because of the coassembly behavior of CNCs and diblock copolymers at the oil/water interface and can stabilize the liquid/liquid interface and endow the interface elastic property. Based on this property, liquid tubule can be generated through injecting CNC aqueous dispersion to copolymer toluene solution. This formation of liquid tubule opens a new platform for the additive manufacturing technique of three-dimensional printing of liquid constructs.

An Analytical Approach for Piled-Raft Foundation Design Based on Equivalent Pier and Raft Analyses by Using 2D Finite Element Method

The piled-raft foundation systems have started to be a very popular design method that is commonly used for especially high-rise buildings. In this foundation system, both raft and piles share the applied loads coming from the supper structures. There are several methods proposed by researchers in order to solve piled-raft foundation problems by simplified methods, approximate methods, and more sophisticated computer-based methods. These sophisticated computer-based solutions are not simply adapted to geotechnical works, and accessing these programs by everyone is not easy. The main purpose of this study is to present an easy and new technique for solving piled-raft problems with using 2D-FEM analysis combined with equivalent pier. In this study, design concepts of a pile-raft system prepared by 2D-FEM analysis combined with equivalent pier were presented. Furthermore, the test results obtained from this method were compared with the results that were taken from equivalent raft method and equivalent pier with single pile response in a sandy soil. A generic example of a piled-raft system including 3 × 3 number piles was designed, and its some properties such as length of pile (10–28 m), pier-soil stiffness ratio (1000–5000), and spacing between the piles (2–4 m) were evaluated and compared as variables. It was concluded from this study that equivalent pier with 2D-FEM analysis can make very similar predictions for calculating settlements of piled-raft system regarding on equivalent pier with single pile response method. As a result of this study: (1) as aspect ratio of piled-raft system increases, raft to pile stiffness ratio gradually increases for all s/d ratios, (2) the efficiency exponents obtained from this study ranges between 0.46 and 0.58 values, (3) stiffness of the piled-raft system gradually increases with increase of slenderness ratio for both two equivalent pier methods, and (4) as slenderness ratio increases, stiffness ratio of the piled-raft system contrarily decreases.

Gracilaria debilis cultivation, agar characterization and economics: bringing new species in the ambit of commercial farming in India

Gracilaria debilis (Forsskal) Borgesen, an economically important red alga, was cultivated for 2 years by a floating bamboo raft method from November 2014 to October 2016 along the southeastern coast of India in order to evaluate possibilities for its year-round cultivation. This was achieved by analyzing biomass yield, growth rate, and agar properties from each harvest. Bench-scale agar characterization and economics were calculated for the first time for G. debilis. Higher biomass yields were recorded during first harvest (November–December) of both the first (11.02 ± 2.08 kg fr.wt m−2) and second (7.17 ± 3.95 kg fr.wt m−2) years. Similarly, higher growth rate was recorded during the first harvest of the first (3.59 ± 0.4% day−1) and second (4.17 ± 0.96% day−1) year, respectively. Biomass yield and DGR were at their minima during monsoon season (i.e., July–August). There was no clear trend pertaining to yield and gel strength of the extracted agar which were in the range of 14–32.6% and 300–866 g cm-2, respectively. This study confirmed that year-round cultivation of G. debilis is possible in Indian waters using the raft culture method with six harvest cycles per annum. The annual income for a single operator was estimated to be US$141, while break-event point per hectare could be achieved after 126 days.

Mild synthesis of environment-friendly thermoplastic triblock copolymer elastomers through combination of ring-opening and RAFT polymerization

Environment-friendly thermoplastic triblock copolymer elastomers, polylactide-block-polyisoprene-block-polylactide, were synthesized by a mild ROP and RAFT method.

Comparing photoswitching of acrylate or methacrylate polymers conjugated with donor–acceptor Stenhouse adducts

Polymers with donor–acceptor Stenhouse adduct (DASA) groups were synthesized using RAFT methods to evaluate the effect of polymer length (20 vs. 100 DP units) and backbone rigidity (acrylate and methacrylate blocks).

Preparation of novel multi-walled carbon nanotubes nanocomposite adsorbent via RAFT technique for the adsorption of toxic copper ions

In the present work, polymer-coated multiwalled carbon nanotube (MWCNT) was prepared via RAFT method. First, a novel trithiocarbonate-based RAFT agent was prepared attached chemically into the surface of MWCNT. In addition, the RAFT co-polymerization of acrylic acid and acrylamide monomers was conducted through the prepared RAFT agent. In the next age, the surface morphology and chemical properties of the prepared components were fully examined by using FTIR, 1HNMR, SEM, TEM, XRD and TGA/DTG techniques. Finally, the modified MWCNT composite was employed as an excellent adsorbent for the adsorption of copper (II) ions. The results indicated that ion adsorption basically relies on adsorbing time, solution pH, initial copper concentration, and adsorbent dosage. Further, the adsorption kinetics and isotherm analysis demonstrated that the adsorption mode was fitted with the pseudo-second-order and Langmuir isotherm models, respectively. Based on the results of thermodynamic study, the ion adsorption process was endothermic and spontaneous. Finally, based on the experimental results, the surface functionalized MWCNT with hydrophilic groups could be successfully used as a promising selective adsorbent material in wastewater treatment.

Synthesis and Characterization of a Nano-Polyplex system of GNRs-PDMAEA-pDNA: An Inert Self-Catalyzed Degradable Carrier for Facile Gene Delivery

Engineering molecules at nano-scale is a promising approach in targeting and curing diseases. In this research, fabricated new hybrid system called nano-polyplex represents an example of the molecular engineering at nano-scale. Polymer of PDMAEAs with four different molecular weights were synthesized using the RAFT method, attached onto the gold nano-rod surface, which modified and produced a safe novel system with an average size less than 100 nm. The hybrid system was characterized by ultra violet-visible spectrophotometer (UV-Vis), dynamic light scattering (DLS), 1H NMR, gel permeation chromatography (GPC), Fourier transform-infrared (FT-IR) spectroscopy, Zeta potential analyzer and transmission electron microscopy (TEM). Features of higher transfection and lower toxicity compared to the previously reported polyplex of PDMAEA, as well as the gold standard PEI, have been shown in all molecular weights and defined N/P ratios (10–200). The ideal physicochemical properties for escaping from the cell barriers, covering the large volume of genetic material (pDNA) and high efficiency of loading polyplexes on GNRs’ surface make it an ideal carrier. The results of this effort pave way in designing a new generation of nanoparticle-based delivery systems for nucleic acid therapy and gene editing.

Method for preparing a well-defined molecularly imprinted polymeric system via radiation-induced RAFT polymerization

RAFT polymerization was utilized to imprint atrazine, a model herbicide, onto porous nonwoven fabric via surface-initiated polymerization of methacrylic acid (MAA) using γ-rays for the generation of radicals. Cumyl dithiobenzoate (CDB) and ethylene glycol dimethacrylate (EGDMA) were employed as the RAFT agent and crosslinker, respectively. The surface-imprinted PE/PP nonwoven fabric was characterized by ATR-FTIR, XPS, SEM and positron annihilation lifetime spectroscopy (PALS). Atrazine uptake measurements were carried out by HPLC. It was demonstrated that RAFT polymerization could be successfully utilized in conjunction with radiation-induced grafting technique for the preparation of well-defined MIPs. The MIP layer grafted onto the surface exhibited the same efficiency through the whole thickness range attained. The MIPs synthesized by RAFT method presented an increase of over 100% in binding capacity at low atrazine feed concentrations compared to those prepared by conventional free-radical polymerization method where no RAFT agent was employed.

Thermo-responsive poly(N-isopropylacrylamide)-block-poly(ionic liquid) of pyridinium sulfonate immobilized Pd nanoparticles in C-C coupling reactions.

A thermo-responsive poly(N-isopropylacrylamide)-block-poly(ionic liquid) (PNIPAM-b-PIL) of pyridinium-type was prepared. Initially, controlled synthesis of PNIPAM was performed via RAFT method. Subsequently, PNIPAM as macromolecular chain transfer agent (macro-CTA) was used for fabrication of PNIPAM-b-PIL through reaction with a synthesized IL monomer i.e. 4-vinyl pyridinium propane sulfonate. The Pd catalyst was produced throughout palladium nanoparticles' anchoring into this block copolymer. The catalyst was characterized using ICP, FT-IR, NMR, UV-Vis, TGA, XRD, SEM and EDX techniques. The catalyst's TEM image proved nearly fine dispersion of PdNPs with negligible agglomeration. The catalyst was used in the production of a variety of substituted alkenes and biaryl compounds (Heck and Suzuki coupling) in organic and aqueous media and under solvent free conditions. Additionally, the results signified extreme reusability of the catalyst with a simple recycling procedure.

Successful establishment of commercial farming of carrageenophyte Kappaphycus alvarezii Doty (Doty) in Sri Lanka: Economics of farming and quality of dry seaweed

Kappaphycus alvarezii seed material was brought from Malaysia in 2011 to initiate cultivation in Sri Lanka. After conducting trial cultivation, the results were found encouraging and commercial farming was started in mid-2012 at Valaipadu village. The average daily growth rates (ADGRs) using bamboo raft method were varied from 3.44 ± 0.12 to 4.45 ± 0.85% in 2014 and 3.47 ± 0.33 to 4.51 ± 0.58% in 2015, whereas using the monoline method, the same were 2.99 ± 71 to 3.95 ± 0.55% in 2014 and 2.44 ± 1.14 to 4.22 ± 0.37% in 2015. ADGR% decreased with increasing seawater temperature (p = −788, r = 0.01) and was positively correlated with water motion (p = 820, r = 0.001). The average monthly production of dry seaweed of a family of three members was 1359 to 1800 kg, and their monthly income ranged between US$465 and 615. The qualities of dry weed produced in 2014 in terms of moisture, clean anhydrous weed, soluble salt, impurities, and C/s ratio were 34.20 ± 3.47, 40.18 ± 3.77, 25.04 ± 2.39, 0.56 ± 0.46, and 1.42 ± 0.35, respectively, whereas in 2015, the values were 34.08 ± 1.81, 39.20 ± 3.62, 25.24 ± 1.90, 1.44 ± 0.50, and 1.46 ± 0.37%. The yield of SRC manufactured at commercial level was 34.64 ± 2.36% and its water and KCl gel strengths were 430 ± 147.88 and 871 ± 166.30 g cm−2, respectively. The absorbance of SRC sample at 1257, 1074, 929, and 846 cm−1 in IR spectrum confirms that it was a kappa kind of carrageenan. Results of commercial cultivation of K. alvarezii in the present investigation showed that Sri Lanka has good potential to create additional income for coastal people through its farming and produce quality dry weed for the carrageenan industries.

Photoresponsive polyelectrolyte/mesoporous silica hybrid materials with remote-controllable ionic transportation

We present a comprehensive research on the photo-induced multi-responsibility of azobenzene(azo) diblock copolymer (BPC) grafted from the surface of mesoporous silica as a light-triggered and controllable ions transport system. The surface-initiated RAFT method was used to grow sequentially a first poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block serving as an inner layer for the pH and thermal responsibility and a second terminal azo block functionalizing the trans-cis photoisomerization to control the closure or opening of the brushes in water. We show that the ions conductivity of hybrid system could be controlled by the second block switchable between the coil-recoil brush chain states in response to pH or temperature change or exposure to light. It was confirmed a suitable composition ratio of azo BPC brushes could significantly influence the hydrophilicity and polarity of the out layer with light, resulting the protonation or gelation of PDMAEMA block. For example, the Ru(NH3)63+ cations as probing ions was employed to prototyping the controlled permselectivity triggered by the UV light exposure. This kind of hybrid material is particularly interesting in the versatile utility for drug delivery, separating, biomimic sensor and so on.

Preparation of well-defined erythromycin imprinted non-woven fabrics via radiation-induced RAFT-mediated grafting

Radiation-induced RAFT polymerization technique was applied to synthesize well-defined molecularly imprinted polymers (MIPs) of erythromycin (ERY). Methacrylic acid (MAA) was grafted onto porous polyethylene (PE)/polypropylene (PP) nonwoven fabrics, under γ-irradiation by employing 2-pheny-2-propyl benzodithioate as the RAFT agent and ethylene glycol dimethacrylate (EGDMA) as the crosslinker. MAA/erythromycin ratios of 2/1, 4/1, 6/1 were tested to optimize the synthesis of MIPs. The highest binding capacity was encountered at a MAA/ERY ratio of 4/1. Non-imprinted polymers (NIPs) were also synthesized in the absence of ERY. The MIPs synthesized by RAFT method presented a better binding capacity compared to those prepared by conventional method where no RAFT agent was employed.

Planar Phase Separation of Weak Polyelectrolyte Brushes in Poor Solvent

ABSTRACTPoly(acrylic acid) (PAA) brushes were synthesized on silicon wafer substrates using a silane linker and Z‐group RAFT method, which enables the controlled variation of brush characteristics. Atomic force microscopy (AFM) was used to characterize the brush morphology in the dry state, which ranged from isolated globules to micelles to a continuous film featuring dimples. Surface morphology was primarily determined by total grafted polymer concentration with a critical polymer concentration between 4.5 and 6.5 × 10−23mol/nm2, where the polymer rich regions transition from micellar islands to a continuous film with dimples. However, even at the highest grafting densities and brush strand lengths used in this study, a flat homogenous film was not formed. Morphological consequences of the solvent and thermal history were shown to persist into poorly solvated state after being dried. X‐ray photoelectron spectroscopy (XPS) was used to quantify the degree of remaining salt after drying. It was found that a higher relative amount of salt was retained after drying in the lower grafting density samples. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 370–377

Selection of potential method for cultivation and seed stock maintenance of Kappaphycus alvarezii during the northeast monsoon in southeast coast of India

Kappaphycus alvarezii (Doty) Doty ex P.C. Silva was cultivated in two different methods, i.e., floating bamboo raft method and floating long line net bag method to study the potential biomass (g FW plant−1), its growth pattern and highest crop yield (kg FW) in northeast monsoon season at Mandapam coast, south east coast of India. Growth data, crop yield, cost, and economics were analyzed. The study was conducted from October 2014 to March 2015. The overall average (of three growth cycles) crop yield obtained after 60 days was 330.00 ± 67.26 kg FW line−1 with DGR of 3.49 ± 0.34 % in floating long line net bag method and 215.56 ± 61.98 kg FW raft−1 with DGR of 2.07 ± 0.44 % in floating bamboo raft method. The net fresh crop yield 7836 kg FW was obtained (in three growth cycles) in floating long-line net bag method and it was 4200 kg FW in floating bamboo raft method and also the margin of safety (47.19 %), return on investment (87.24 %), and profit margin (46.59 %) were higher in floating long line net bag method than floating bamboo raft method. Hence, the floating long line net bag method is more efficient and economically superior to floating bamboo raft method for seed stock maintenance and commercial cultivation during northeast monsoon, which enables year round cultivation at southeast coast of India.

Does orientation of raft helps in augmenting yield during lean period?: A case study of Gracilaria edulis cultivation in open sea by vertical raft alignment along the south-eastern coast of India

The food grade agar in India has been almost exclusively obtained from Gracilaria edulis, but the industrial production overwhelmingly relies on exploitation of natural resources. United Nations efforts through Food and Agriculture Organization under Bay of Bengal Program highlighted the necessity of undertaking commercial farming of this species along Indian coast for socio-economic benefits. The pilot-scale experiments established viability of large-scale cultivation by floating raft method. Nevertheless, drastic reduction in yield and quality during summer months due to enhanced sedimentation and severe epiphytism is found to be a major hindrance. Altering the positioning of rafts from horizontal to vertical alignment improved the growth and yield under open sea condition at two different locations along south east coast of India. The average yield in horizontal raft was found to be 3.08±0.61kgfrwtraft−1 with corresponding DGR of 1.87±0.63% day−1 while same in case of vertical rafts was 13.76±3.86kgfrwtraft−1 and 5.00±0.5% day−1 in Gulf of Mannar under 45days growth cycle. The corresponding values along Palk Bay were 2.98±0.52gfrwtraft−1 and 1.38±0.42% day−1 for horizontal raft and 13.02±6.06kgfrwtraft−1 and 4.14±1.18% day−1 for vertical raft. ANOVA clearly indicated that raft position significantly influenced the biomass yield and DGR at Palk Bay (F=75.77; F=112.81) as well as Gulf of Mannar (F=27.21; F=59.16) at p=0.001. The increment of 1.9–2.6% in fresh weight of individual frond was reported in vertically aligned rafts. The computational fluid dynamics (CFD) based unsteady numerical simulations have confirmed that vertical alignment of raft facilitates relatively free movement of water due to which sedimentation and epiphytism are either minimised or eliminated. Thus these studies can help us to deduce important conclusions pertaining to management of sustained commercial cultivation of this alga in Indian waters.