The subnano free‐volume hole features of Nafion‐212 and poly(styrene sulfonic acid) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes are investigated by using the positron annihilation lifetime spectroscopic analyses with three‐ and four‐component models (i.e., one‐ and two‐ortho‐positronium [o‐Ps] components). The four‐component model provides a more adequate description of free‐volume hole features for both membranes, in which the longer o‐Ps lifetime is assigned to the larger free volume hole sizes in the mobile side chains, while the shorter o‐Ps lifetime is associated with the smaller free volume hole sizes within the backbones (the rigid amorphous fractions and the crystalline‐amorphous interfaces) and the interfaces between the main chains and the side chains. The o‐Ps annihilation is found to occur primarily in the side chains. The subnano volume hole features revealed by the positron annihilation lifetime (PAL) spectra suggest the primary water uptake and conductance in the side chains and the possible presence of water molecules in the rigid amorphous fractions and the interfaces. Note that the three‐component model as usually reported in the literature may underestimate the lifetime and intensity of ortho‐positronium annihilation.

Free and Open Indo-Pacific (FOIP) is considered a U.S. strategy to deal with China and maintain and expand its influence in the Indo-Pacific region. Though FOIP is considered an initiative of the United States, implementing it successfully requires the participation of the Quad including United States, India, Japan and Australia. Besides the Quad, other factors coming from the developing economies of the region will be indispensable components of FOIP. The article gives an overview of the FOIP as well as analyses the stands of ASEAN and Vietnam on this strategy from the perspective of the Vietnamese scholars.

The subnano level free‐volume hole features of poly(styrene sulfonic acid) (PSSA) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs) are investigated using positron annihilation lifetime spectroscopy (PALS). The hole sizes are formed mainly at the graft‐polymerization step and are not altered dramatically at the sulfonation. With increasing grafting degree, τ4, standing for the annihilation of ortho‐positronium (o‐Ps) in the larger free‐volume holes of the mobile amorphous layers and the PSSA grafts outside of the lamellae, decreases monotonously, whereas τ3, representing for that in the smaller free‐volume holes of the lamellar amorphous regions, the PSSA grafts, and the interface zones inside the lamellae, only shows a slight decrease. From the viewpoint of free‐volume hole sizes, gas molecules are predicted to pass dominantly through the mobile amorphous phases and the PSSA grafts outside of the lamellae. Specifically, the limited hole concentration induced by confining lamellae at the interfacial zones is observed. Thus, the obtained results are associated with a significant reduction of gas passing and the moderate or higher tensile strength for the ETFE‐PEMs in comparison to Nafion‐212.

The extensive ultrasmall-angle X-ray scattering measurements are performed in order to investigate the changes of lamellar grains of poly(styrenesulfonic acid)-grafted poly(ethylene-co-tetrafluoroethylene) polymer electrolyte membranes (ETFE-PEMs) that occur during the alteration of grafting degree (GD) under dry and immersed conditions. The lamellar grains of three series of the samples (polystyrene-grafted ETFE films and dry and hydrated ETFE-PEMs) are formed during the grafting process and develop independently with the change of the lamellar stacks. Interestingly, three series of samples exhibit a very similar trend of lamellar grain at any GD and a significant amount of graft chains is observed directly in the region between the grains (GD £ 59%) and outside of the grain network structures (GD > 59%). This observation indicates: i) The formation of the lamellar grains; ii) The rapid changes in characteristic sizes of the lamellar grains compared with the lamellar stacks; and iii) The newly generated phases consisting of only the graft materials. These findings explain why the lamellar grains and the graft chains play an important role in the higher proton conductivity and compatible tensile strengths of the membranes, compared with Nafion, at the immersed and severe operating conditions.

Chemical degradation in the presence of H2O2 aqueous solution and water states of poly(styrene sulfonic acid) (PSSA) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs) with grafting degree (GD) of 8.8%–21.1% are investigated using Fourier‐transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), and electrochemical impedance spectroscopy (EIS). The ETFE‐PEMs show the complete detachment at the α‐hydrogen atoms of the whole graft PSSA chains from the ETFE backbones, while their precursor polystyrene‐grafted ETFE films do not. This chemical degradation exhibits independently with GDs and takes place even at very low GD (<10%). Water molecules of the membranes dried at 40°C are not completely de‐absorbed. The remains are partial non‐bonded water molecules, which are assumed to locate within the lamellar amorphous domains (constrained water molecules) of the crystalline phases. These constrained water molecules exist independently with the PSSA groups and do not detach together with them during the degradation. Note that the water molecules remained at 40°C show the additional contribution of 18%–19% to the total water uptake but do not contribute clearly to the conductance.

India and Myanmar are two neighboring countries that share the border of nearly 1.500km and have the relationship on history, politics, culture, ethnic... from over 2.000 years to present. India officially established diplomatic relations with Myanmar, just after this Southeast Asian country gained independence (1948). From 1948 to 1992, the bilateral relationship was influenced by India’s foreign policy towards Myanmar, especially the impact of “idealism” and “realism” in India’s policy. “Idealism” succeeded in India’s foreign policy towards Myanmar from 1948 to 1962; however, it was not effective in the period 1962 - 1988, which made India’s position severely decrease, contrary to the rise of China’s position in Myanmar. For this reason, India must innovate the foreign thought, moving from “idealism” to “realism”, which have more pragmatic quality to Myanmar in the years 1988 - 1992 when the international and regional contexts have many changes. On the basis of the reference sources, this research’s aim focuses on analyzing the foreign policy adjustment of India, especially this study will focus on the issue of India - Myanmar relationship (1948 - 1992) was dominated by the “idealism” and “realism” in the planning of foreign policy of India towards Myanmar. The scope of this research is the relationship between India and Myanmar from 1948 to 1992 under the influence of “idealism” and “realism” in India’s foreign policy. From the early 90s of the 20th century, India’s foreign policy towards Myanmar has been more realistic than in the previous period, especially since 1992, when India implemented its new foreign policy, the Look East Policy.   Received: 4 February 2021 / Accepted: 9 April 2021 / Published: 10 May 2021

Maritime security has been in recent times emerged as a burning issue in the fields of international relations in general and in the Indo-Pacific region in particular. With topographical tectonics, this area includes numerous “choke points” on maritime routes that are strategically important to world trade, playing an important role in the transportation of oil, gas and cargo products from the Middle East to Australia and East Asia. Therefore, maritime security issues for the lifeline of the world economy are concerned by the countries in the Indo-Pacific region, in which the important role of the sea route through Straits of Malacca is increasingly emphasized. With a geostrategic position connecting the Andaman Sea (Indian Ocean) and the South China Sea (Pacific Ocean), Straits of Malacca is the shortest route between the Middle East and Asia in general and Pacific Rim countries in particular. This is the location that accounts for a quarter of the world’s marine traffic annually. Energy security and trade economy of major powerful countries in the Indo-Pacific region depend heavily on the maritime security of Straits of Malacca route. Through an analysis of the Malacca Strait’s geostrategic location, this paper elucidates the Indo-Pacific region’s importance in maritime security field in the first two decades of the twenty-first century.

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