View source for Chemistry:Latex

{{short description|Stable dispersion of polymer microparticles in an aqueous medium}}

[[File:Latex-production.jpg|thumb|Tapping of latex from a tree, for use in rubber production]]

'''Latex''' is an [[Chemistry:Emulsion|emulsion]] (stable dispersion) of [[Chemistry:Polymer|polymer]] [[Medicine:Microparticle|microparticle]]s in water.<ref>{{cite journal |doi=10.1080/15583724.2013.776586|title=Homogeneous Hydrogenation Art of Nitrile Butadiene Rubber: A Review|year=2013|last1=Wang|first1=Hui|last2=Yang|first2=Lijuan|last3=Rempel|first3=Garry L.|journal=Polymer Reviews|volume=53|issue=2|pages=192–239|s2cid=96720306}}</ref> Latexes are found in [[Earth:Nature|nature]], but synthetic latexes are common as well.

In nature, latex is found as a milky [[Physics:Fluid|fluid]], which is present in 10% of all [[Biology:Flowering plant|flowering plant]]s (angiosperms).<ref name="Agrawal">{{cite journal |author1=Anurag A. Agrawal |author2=d Kotaro Konno |date=2009 |title=Latex: a model for understanding mechanisms, ecology, and evolution of plant defense Against herbivory |journal=Annual Review of Ecology, Evolution, and Systematics |volume=40 |pages=311–331 |doi=10.1146/annurev.ecolsys.110308.120307}}</ref> It is a complex emulsion that coagulates on exposure to air, consisting of [[Biology:Protein|protein]]s, [[Chemistry:Alkaloid|alkaloid]]s, [[Chemistry:Starch|starch]]es, [[Chemistry:Sugar|sugar]]s, oils, [[Chemistry:Tannin|tannin]]s, resins, and [[Chemistry:Natural gum|gum]]s. It is usually exuded after tissue injury. In most plants, latex is white, but some have yellow, orange, or scarlet latex. Since the 17th century, latex has been used as a term for the fluid substance in plants, deriving from the [[Social:Latin|Latin]] word for "liquid".<ref>{{cite journal |author=Paul G. Mahlberg |date=1993 |title=Laticifers: an historical perspective |journal=The Botanical Review |volume=59 |issue=1 |pages=1–23 |jstor=4354199 |doi=10.1007/bf02856611|s2cid=40056337 }}</ref><ref>{{OEtymD|latex}}</ref><ref>{{L&S|latex|ref}}</ref> It serves mainly as defense against herbivorous [[Biology:Insect|insect]]s.<ref name="Agrawal"/> Latex is not to be confused with plant sap; it is a distinct substance, separately produced, and with different functions.

The word latex is also used to refer to natural latex [[Chemistry:Rubber|rubber]], particularly non-[[Chemistry:Vulcanization|vulcanized]] rubber. Such is the case in products like latex [[Engineering:Glove|glove]]s, latex [[Medicine:Condom|condom]]s, latex clothing, and balloons.

{{Quote box
| width = 50%
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| title = [[Organization:International Union of Pure and Applied Chemistry|IUPAC]] definition.
| quote = '''Latex''': [[Physics:Colloid|Colloid]]al dispersion of polymer particles in a liquid.<ref name="terminology">{{cite journal |author1=Stanislaw Slomkowski |author2=José V. Alemán |author3=Robert G. Gilbert |author4=Michael Hess |author5=Kazuyuki Horie |author6=Richard G. Jones |author7=Przemyslaw Kubisa |author8=Ingrid Meisel |author9=Werner Mormann |author10=Stanisław Penczek |author11=Robert F. T. Stepto |date=2011 |title=Terminology of polymers and polymerization processes in dispersed systems (IUPAC Recommendations 2011) |journal=[[Chemistry:Pure and Applied Chemistry|Pure and Applied Chemistry]] |volume=83 |issue=12 |pages=2229–2311 |doi=10.1351/PAC-REC-10-06-03 |s2cid=96812603 |url= http://pac.iupac.org/publications/pac/pdf/2011/pdf/8312x2229.pdf |url-status=live |archive-url= https://web.archive.org/web/20131020164408/http://pac.iupac.org/publications/pac/pdf/2011/pdf/8312x2229.pdf |archive-date=2013-10-20 }}</ref>{{efn|The polymer in the particles may be organic or inorganic.<ref name="terminology"/>}}<br/>
'''Synthetic latex''': Latex obtained as a product of an [[Chemistry:Emulsion polymerization|emulsion]], mini-emulsion, micro-emulsion, or [[Chemistry:Dispersion polymerization|dispersion polymerization]].<ref name="terminology"/>
}}

==Biology==

===Articulated laticifers===
The [[Biology:Cell|cells]] ([[Biology:Laticifer|laticifer]]s) in which latex is found make up the laticiferous system, which can form in two very different ways. In many plants, the laticiferous system is formed from rows of cells laid down in the [[Biology:Meristem|meristem]] of the [[Biology:Plant stem|stem]] or [[Biology:Root|root]]. The [[Biology:Cell wall|cell wall]]s between these cells are dissolved so that continuous tubes, called latex vessels, are formed. Since these vessels are made of many cells, they are known as ''articulated laticifers''. This method of formation is found in the [[Biology:Papaveraceae|poppy family]] and in the [[Chemistry:Rubber|rubber]] trees ([[Biology:Hevea brasiliensis|Para rubber tree]], members of the family [[Biology:Euphorbiaceae|Euphorbiaceae]], members of the [[Biology:Moraceae|mulberry and fig family]], such as the Panama rubber tree ''[[Biology:Castilla elastica|Castilla elastica]]''), and members of the family [[Biology:Asteraceae|Asteraceae]]. For instance, ''[[Biology:Parthenium argentatum|Parthenium argentatum]]'' the guayule plant, is in the tribe [[Biology:Heliantheae|Heliantheae]]; other latex-bearing Asteraceae with articulated laticifers include members of the [[Biology:Cichorieae|Cichorieae]], a [[Biology:Clade|clade]] whose members produce latex, some of them in commercially interesting amounts. This includes ''[[Biology:Taraxacum kok-saghyz|Taraxacum kok-saghyz]]'', a species cultivated for latex production.<ref>{{cite web |url=http://www.pfaf.org/user/Plant.aspx?LatinName=Taraxacum+kok-saghyz |title=Taraxacum kok-saghyz |publisher=Pfaf.org |access-date=2013-03-21 |url-status=live |archive-url=https://web.archive.org/web/20140320155113/http://www.pfaf.org/user/Plant.aspx?LatinName=Taraxacum+kok-saghyz |archive-date=2014-03-20 }}</ref>

===Non-articulated laticifers===
In the [[Biology:Asclepiadaceae|milkweed]] and [[Biology:Euphorbiaceae|spurge]] families, on the other hand, the laticiferous system is formed quite differently. Early in the development of the seedling, latex cells differentiate, and as the plant grows these latex cells grow into a branching system extending throughout the plant. In many [[Biology:Euphorbiaceae|euphorbs]], the entire structure is made from a single cell – this type of system is known as a ''non-articulated laticifer'', to distinguish it from the multi-cellular structures discussed above. In the mature plant, the entire laticiferous system is descended from a single cell or group of cells present in the [[Biology:Embryo|embryo]].

The laticiferous system is present in all parts of the mature plant, including roots, stems, [[Biology:Leaf|leaves]], and sometimes the [[Biology:Fruit|fruit]]s. It is particularly noticeable in the [[Biology:Cortex (botany)|cortical]] tissues. Latex is usually exuded as a white liquid, but is some cases it can be clear, yellow or red, as in [[Biology:Cannabaceae|Cannabaceae]].<ref name="Agrawal"/>

==Productive species==
Latex is produced by 20,000 [[Biology:Flowering plant|flowering plant]] species from over 40 families. These include both dicots and monocots. Latex has been found in 14 percent of tropical plant species, as well as six percent of temperate plant species.<ref>{{cite journal |author=Thomas M. Lewinsohn |date=1991 |title=The geographical distribution of plant latex |journal=Chemoecology |volume=2 |issue=1 |pages=64–68 |doi=10.1007/BF01240668|s2cid=44594197 }}</ref> Several members of the fungal kingdom also produce latex upon injury, such as ''[[Biology:Lactarius deliciosus|Lactarius deliciosus]]'' and other milk-caps. This suggests it is the product of [[Biology:Convergent evolution|convergent evolution]] and has been selected for on many separate occasions.<ref name="Agrawal"/>

==Defense function==
[[File:Latex being collected from a tapped rubber tree.jpg|thumb|Rubber tapping latex]]

Latex functions to protect the plant from herbivores. The idea was first proposed in 1887 by Joseph F. James, who noted that latex of [[Biology:Asclepias syriaca|milkweed]] <blockquote>carries with it at the same time such disagreeable properties that it becomes a better protection to the plant from enemies than all the thorns, prickles, or hairs that could be provided. In this plant, so copious and so distasteful has the sap become that it serves a most important purpose in its economy.<ref>{{cite journal |author=Joseph F. James |date=1887 |title=The milkweeds |journal=[[Biology:The American Naturalist|The American Naturalist]] |volume=21 |issue= 7|pages=605–615 |jstor=2451222 |url=https://archive.org/stream/jstor-2451222/2451222 |doi=10.1086/274519|doi-access=free }}</ref></blockquote> 
Evidence showing this defense function include the finding that [[Biology:Slug|slug]]s will eat leaves drained of their latex but not intact ones, that many insects sever the veins carrying latex before they feed, and that the latex of ''[[Biology:Asclepias humistrata|Asclepias humistrata]]'' (sandhill milkweed) kills by trapping 30% of newly hatched [[Biology:Monarch butterfly|monarch butterfly]] caterpillars.<ref name="Agrawal"/>

Other evidence is that latex contains 50–1000× higher concentrations of defense substances than other plant tissues. These toxins include ones that are also toxic to the plant and consist of a diverse range of chemicals that are either poisonous or "antinutritive."

Latex is actively moved to the area of injury; in the case of ''[[Biology:Cryptostegia grandiflora|Cryptostegia grandiflora]]'', latex more than 70&nbsp;cm from the site of injury is mobilized.<ref name="Agrawal" /> The large hydrostatic pressure in this vine enables an extremely high flow rate of latex. In a 1935 report the botanist Catherine M. Bangham observed that "piercing the fruit stalk of ''Cryptostegia grandiflora'' produced a jet of latex over a meter long, and maintained [this jet] for several seconds."<ref>{{Cite book |last=Buttery |first=R. R. |title=Water Deficits and Plant Growth, Volume IV: Soil Water Measurement, Plant Responses, and Breeding for Drought Resistance |last2=Boatman |first2=S. G. |publisher=Academic Press, Inc. |year=1976 |isbn=978-0124314269 |editor-last=Kozlowski |editor-first=T. T. |edition=1st |volume=IV |location=New York, New York 10003 |pages=252 |language=english}}</ref>

The clotting property of latex is functional in this defense since it limits wastage and its stickiness traps insects and their mouthparts.<ref name="Agrawal"/>

While there exist other explanations for the existence of latex including storage and movement of plant nutrients, waste, and maintenance of water balance that "[e]ssentially none of these functions remain credible and none have any empirical support".<ref name="Agrawal"/>

==Applications==
[[File:Opium pod cut to demonstrate fluid extraction1.jpg|thumb|upright|[[Biology:Papaver somniferum|Opium poppy]] exuding fresh latex from a cut]]

The latex of many species can be processed to produce many materials.

* Balatá and gutta percha latex contain an inelastic polymer related to rubber.{{Citation needed|date=March 2021}}
* [[Biology:Chicle|Chicle]] and [[Biology:Dyera costulata|jelutong]] tree latex was used in chewing gum.<ref name=Mathews>{{cite book|last=Mathews|first=Jennifer P.|title=Chicle: The chewing gum of the Americas, from the ancient Maya to William Wrigley|date=2009|publisher=University of Arizona Press|location=Tucson|isbn=978-0-8165-2821-9}}</ref>

===Personal and healthcare products===
[[Chemistry:Natural rubber|Natural rubber]] is the most important product obtained from latex; more than 12,000 plant species yield latex containing rubber, though in the vast majority of those species the rubber is not suitable for commercial use.<ref name='Bowers'>{{cite book |author=J. E. Bowers |date=1990 |title=Natural Rubber-Producing Plants for the United States |url=https://archive.org/details/CAT91942814 | publisher=National Agricultural Library |location=Beltsville, MD |oclc=28534889 |pages=[https://archive.org/details/CAT91942814/page/1 1], 3}}</ref> This latex is used to make many other products including mattresses,<ref>{{cite web |last1=Liman |first1=Stacy |title=Latex Mattresses: The Best Latex Mattress Guide |date=26 June 2020 |url=https://amerisleep.com/blog/latex-mattresses/ |access-date=17 August 2020}}</ref><ref>{{Cite web|last=Yurkovich|first=Dror|title=Dunlop latex vs. Talalay latex|url=https://getha.co.il/%d7%9e%d7%96%d7%a8%d7%a0%d7%99-%d7%a7%d7%a6%d7%a3-%d7%9e%d7%94%d7%99-%d7%a9%d7%99%d7%98%d7%aa-%d7%94%d7%99%d7%99%d7%a6%d7%95%d7%a8-%d7%94%d7%9e%d7%94%d7%a4%d7%9b%d7%a0%d7%99%d7%aa-%d7%a9%d7%9c-%d7%92/|url-status=dead|website=Getha|access-date=2021-04-22|archive-date=2021-04-13|archive-url=https://web.archive.org/web/20210413125251/https://getha.co.il/%D7%9E%D7%96%D7%A8%D7%A0%D7%99-%D7%A7%D7%A6%D7%A3-%D7%9E%D7%94%D7%99-%D7%A9%D7%99%D7%98%D7%AA-%D7%94%D7%99%D7%99%D7%A6%D7%95%D7%A8-%D7%94%D7%9E%D7%94%D7%A4%D7%9B%D7%A0%D7%99%D7%AA-%D7%A9%D7%9C-%D7%92/}}</ref> [[Engineering:Glove|glove]]s, swim caps, [[Medicine:Condom|condom]]s, [[Medicine:Catheter|catheter]]s and balloons.{{Citation needed|date=March 2021}}

===Opium and opiates===
Dried latex from the [[Biology:Papaver somniferum|opium poppy]] is called [[Biology:Opium|opium]], the source of several useful [[Biology:Analgesic|analgesic]] [[Chemistry:Alkaloid|alkaloid]]s such as [[Chemistry:Codeine|codeine]], [[Chemistry:Thebaine|thebaine]], and [[Biology:Morphine|morphine]], the latter two of which can then further be used in the synthesis and manufacture of other (typically stronger) opioids for medicinal use, and of [[Chemistry:Heroin|heroin]] for the [[Finance:Illegal drug trade|illegal drug trade]]. The opium poppy is also the source of medically useful non-analgesic alkaloids, such as [[Chemistry:Papaverine|papaverine]] and [[Chemistry:Noscapine|noscapine]].{{Citation needed|date=March 2021}}

===Clothing===

Latex is used in many types of clothing. Worn on the body (or applied directly by painting), it tends to be skin-tight, producing a "second skin" effect.<ref>{{Cite book|url=https://www.worldcat.org/oclc/1262726608|title=Kink and everyday life : interdisciplinary reflections on practice and portrayal|date=2021|others=Kylo-Patrick R. Hart, Teresa Cutler-Broyles|isbn=978-1-83982-918-5|edition=|location=Bingley|oclc=1262726608}}</ref>

===Industrial and biological applications of synthetic latexes===
Synthetic latexes are used in [[Physics:Coating|coating]]s (e.g., latex paint) and glues because they solidify by [[Chemistry:Coalescence|coalescence]] of the polymer particles as the water evaporates. These synthetic latexes therefore can form films without releasing potentially toxic organic solvents in the environment. Other uses include cement additives and to conceal information on scratchcards. Latex, usually [[Chemistry:Styrene|styrene]]-based, is also used in [[Biology:Immunoassay|immunoassay]]s.<ref>{{Cite journal |last=Akamine |first=Y. |last2=Sato |first2=S. |last3=Kagaya |first3=H. |last4=Ohkubo |first4=T. |last5=Satoh |first5=S. |last6=Miura |first6=M. |date=2018-04-20 |title=Comparison of electrochemiluminescence immunoassay and latex agglutination turbidimetric immunoassay for evaluation of everolimus blood concentrations in renal transplant patients |url=https://onlinelibrary.wiley.com/doi/10.1111/jcpt.12686 |journal=Journal of Clinical Pharmacy and Therapeutics |language=en |volume=43 |issue=5 |pages=675–681 |doi=10.1111/jcpt.12686 |issn=0269-4727|doi-access=free }}</ref>

==Allergic reactions==
{{Main article|Medicine:Latex allergy}}
Some people only experience a [[Medicine:Allergy|mild allergy]] when exposed to latex, like eczema, contact dermatitis or developing a rash.<ref>{{Cite web|url=https://acaai.org/allergies/types/latex-allergy|title=Latex Allergy {{!}} Causes, Symptoms & Treatment|website=ACAAI Public Website|language=en|access-date=2019-03-24}}</ref>

Others have a serious [[Medicine:Latex allergy|latex allergy]], and exposure to latex products such as latex gloves can cause anaphylactic shock. [[Chemistry:Guayule|Guayule]] latex has only 2% of the levels of protein found in ''[[Biology:Hevea|Hevea]]'' latexes, and is being researched as a lower-allergen substitute.<ref>{{cite book|url=https://books.google.com/books?id=De9RUVtQ5TQC&q=artificial+polyisoprene+protein&pg=PA33|title=Emulsion Polymerisation and Latex Applications|first1=Christopher D.|last1=Anderson|first2=Eric S.|last2=Daniels|date=8 May 2018|publisher=iSmithers Rapra Publishing|isbn=9781859573815|access-date=8 May 2018|via=Google Books}}</ref> Additionally, chemical processes may be employed to reduce the amount of antigenic protein in ''Hevea'' latex, yielding alternative materials such as Vytex Natural Rubber Latex which provide significantly reduced exposure to latex allergens.

About half of people with [[Medicine:Spina bifida|spina bifida]] are also allergic to natural latex rubber, as well as people who have had multiple surgeries, and people who have had prolonged exposure to natural latex.<ref>{{cite web|url=http://www.mayoclinic.com/health/latex-allergy/DS00621/DSECTION=risk-factors|title=Latex allergy - Symptoms and causes|website=mayoclinic.com|access-date=8 May 2018|url-status=live|archive-url=https://web.archive.org/web/20131007231835/http://www.mayoclinic.com/health/latex-allergy/DS00621/DSECTION=risk%2Dfactors|archive-date=7 October 2013}}</ref>

===Microbial degradation===
Several species of the microbe genera ''[[Biology:Actinomycetota|Actinomycetes]]'', ''[[Biology:Streptomyces|Streptomyces]]'', ''[[Biology:Nocardia|Nocardia]]'', ''[[Biology:Micromonospora|Micromonospora]]'', and ''[[Biology:Actinoplanes|Actinoplanes]]'' are capable of consuming rubber latex.<ref>{{cite journal|journal=Applied and Environmental Microbiology|title=Physiological and Chemical Investigations into Microbial Degradation of Synthetic Poly(cis-1,4-isoprene)|author1=Helge B. Bode|author2= Axel Zeeck|author3=Kirsten Plückhahn|author4=Dieter Jendrossek|date=September 2000|volume=66|issue=9|doi=10.1128/aem.66.9.3680-3685.2000|pages=3680–3685|pmid=10966376|pmc=92206|bibcode=2000ApEnM..66.3680B}}</ref> However, the rate of biodegradation is slow, and the growth of bacteria utilizing rubber as a sole carbon source is also slow.<ref>{{cite journal|last1=Rose|first1=K.|last2=Steinbuchel|first2=A.|title=Biodegradation of Natural Rubber and Related Compounds: Recent Insights into a Hardly Understood Catabolic Capability of Microorganisms|journal=Applied and Environmental Microbiology|date=2 June 2005|volume=71|issue=6|pages=2803–2812|doi=10.1128/AEM.71.6.2803-2812.2005|pmc=1151847|pmid=15932971|bibcode=2005ApEnM..71.2803R}}</ref>

==See also==
*Latex clothing
*[[Chemistry:Natural rubber|Natural rubber]]
*{{C|Rubber|Rubber−related topics}}

==References==
===Footnotes===
{{Notelist}}

===Notes===
{{Reflist}}

==External links==

{{Non-timber forest products}}


[[Category:Materials]]
[[Category:Rubber]]

{{Sourceattribution|Latex}}