chinese bound trisyllabic morphemes
I know from experience that linguists and grammarians absolutely refuse to define the terms they use adequately in order to build their own cloud castles.

Given the definition:


  morpheme:  a speech element having a meaning or grammatical function
  that cannot be subdivided into further such elements


or:  


  morpheme: "smallest meaningful unit in a language," 1896, from German morpheme,
  coined 1895 by Polish-born linguist Jan Baudouin de Courtenay
  (1845-1929), from Greek morphe "form, shape"


isn't a bound morpheme a contradiction in terms, since it cannot stand alone? Better to use the word 'affix', because that is what is meant.

If you then say: "But a meaningless morpheme may still have a grammatical function." then any letter is a morpheme, since, if I remove, say, 'o' from 'morpheme' I get 'mrpheme'. Therefore, 'o' has the grammatical function of making 'mrpheme' an interpretable  collection of letters. Thus the smallest morpheme in English is a letter and smaller than a letter you cannot write.

In another thread someone complained about the arrogant insistence that Western grammatical concepts must also be applicable to Chinese. I wholeheartedly agree. Most, if not all, of the precepts of Western Grammar have no scientific definition, but people talk about them as if they were scientific facts which must also be true in Chinese. Can you define 'word' or 'subject' or 'sentence' rigorously? You know what you mean until I ask you to make your definition unequivocal.

Consider the Chinese word: 轿车。

轿jiao4 has 2 or 3 syllables, depending on your point of view.

轿 is made up of: 车 + 乔 （ 夭 + 儿） in Simplified Chinese or 车 + 夭 + 高 in Traditional Chinese.

We could argue 高 is not a morpheme, but I would accept it as such, as a picture of a tall building.

Tang Ho mentioned 们， but this is 人 + 门, so it is not elemental.

I would therefore agree with Tang Ho that Chinese has no bound trisyllabic morphemes and go further and say that neither does English. English has letters and Chinese has Primitives.