## 1 Introduction  
Natural rubber (NR) is an important renewable biopolymer in many industries due to its elastic property and excellent mechanical strength. NR latex is known as a diene rubber in its repeating units of cis-1,4-isoprene, with the molecular weight varying greatly, from only a few hundred thousand to more than one million [1]. The NR can be degraded to liquid natural rubber (LNR), which has a similar microstructure to NR and consists of shorter polymeric chains and lower molecular weight (M\({}_{\rm w}\) < 10\({}^{5}\)) [2]. It becomes a modified NR, allowing greater flexibility in the production of the NR used. LNR produced from the degradation of NR latex is related to breaking the NR chain either by direct scission of the carbon-carbon single or carbon-carbon double bonds of the polyisoprene backbone. The molecular weight of NR can be reduced by different methods such as mechanical, photochemical, ozonolysis, or thermal degradation in a dry, solution, or latex state. Mechanical degradation of NR through mastication in the air at high temperatures is usually done before processing to facilitate easy processing or incorporation of other chemicals [3]. [PERSON] et al. [4] prepared the degraded NR latex under UV light in the presence of H\({}_{2}\)O\({}_{2}\) and nano TiO\({}_{2}\), which was prepared via the sol-gel method. The NR chains were attacked by radicals at carbon-carbon single bond or oxidation at carbon-carbon double bond by oxygen species. LNR containing hydroxyl and carbonyl end groups was observed, resulting from chain breaking. [PERSON] et al. [5] synthesized the deproteinized LNR with hydroxyl end groups by the photochemical reaction. This reaction was carried out through photocatalytic decomposition of H\({}_{2}\)O\({}_{2}\) when exposed to UV light, with or without a TiO\({}_{2}\) film mounted on the quartz substrate. LNR was used as a compatibilizer in NR/LLDPE (linear low-density polyethylene) blends [6; 7; 8]. [PERSON] et al. [6] observed the effects of various molecular weights of LNR as a compatibilizer on the physical properties of NR/LLDPE blends. The ultraviolet irradiation technique was used to prepare LNR. Adding LNR to the blends improved the interaction between the phase of the blends, and they concluded that the LNR content added to the blends marginally affected the physical properties of NR/LLDPE blends. Moreover, LNR with a molecular weight below 20,000 g/mol is an attractive material for enhancement of further modifications. The potential application of LNR with functional end groups is used as a precursor for new material. The authors of [9; 10; 11] prepared flexible foam from poly(\(\varepsilon\)-caprolactone) diol (PCL) and hydroxyl telechelic NR (HTNR). First, carbonyl telechelic NR (CTNR) was prepared by an oxidative chain cleavage reaction in tetrahydrofuran with periodic acid. After that, sodium borohydride was then used to change the LNR with carbonyl end group (CTNR) into LNR with hydroxyl end group (HTNR). They claimed that HTNR-based polyurethane foams had improved elastic properties and low-temperature flexibility compared to foam based on commercial polyol. LNR with a carboxyl termination and its subsequent application in NBR compounds as a reactive polymeric plasticizer was described by [PERSON] et al. [12]. They found that during sulfur vulcanization, the natural rubber component of the carboxyl terminated LNR attacked the NBR. Consequently, this plasticizer was neither volatile nor extractable. [PERSON] and [PERSON] [13] studied the use of gel permeation chromatography (GPC) and Fourier transform infrared (FTIR) spectroscopy to follow the kinetics of chain scission and major changes in functional groups of NR during ozonolysis in chloroform at 0 \({}^{\circ}\)C. They reported that the introduction of a variety of oxygenated functional groups accompanied the reduction in molecular weight of NR during ozonolysis.